Dissertations / Theses on the topic 'Oil fields – Production methods'

Orientador: Celso Kazuyuki Morooka
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
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Resumo: O desenvolvimento de campos marítimos de petróleo e gás natural tem se deslocado para águas cada vez mais profundas, ambientes cada vez mais hostis e áreas cada vez mais remotas. A utilização de soluções convencionais para desenvolver tais campos, especialmente o uso exclusivo de processamento primário em superfície e equipamentos elevação artificial instalados dentro de poços pode não justificar os investimentos. O processamento submarino tem aumentado a atratividade ou até viabilizando a produção de campos marítimos. Visto o aumento em sua utilização, os autores propuseram uma metodologia para selecionar conceitos de plantas submarinas para campos de petróleo e gás natural, utilizando informações disponíveis na literatura e suporte de especialistas em tecnologia submarina e modelagem de produção integrada. Uma menor contrapressão no poço produtor é uma potencial consequência do uso de processamento submarino, podendo tornar o perfil de produção mais atrativo. Como consequência, uma abordagem integrada considerando os estudos necessários para avaliar o escoamento dos fluidos de suas fontes iniciais até os destinos finais é necessária para se propor uma metodologia de seleção. Como alternativa à falta de estudos integrados comparando diferentes soluções de desenvolvimento em campos marítimos, informações de quatro desenvolvimentos comerciais que empregaram processamento submarino foram utilizadas para buscar a validação da metodologia. Os resultados destes estudos de caso sugerem que a metodologia é válida, entretanto não é claro que tais desenvolvimentos de produção utilizariam todas as fases propostas
Abstract: The development of offshore oil and natural gas fields has been moving to deeper waters, harsher environments and more remote areas. The use of conventional solutions to develop such fields, especially sole use of surface processing or downhole artificial lift methods, may not justify the investments. Subsea processing has been increasing the attractiveness or even enabling offshore field developments. Given the increase in its use, the authors proposed a methodology to select concepts of subsea processing plants for oil and natural gas fields, using information available in the literature as well as support from specialists in subsea technology and integrated production modelling. Higher drawdown in producer wells is a potential consequence of the use of subsea processing, therefore it may positively impact the production profile. As a consequence, an integrated approach comprising all the studies necessary to assess the flow between the initial sources and the final destinations is necessary to propose a selection methodology. As an alternative to overcome the lack of integrated studies comparing different development solutions in offshore fields, information from four commercial developments that employed subsea processing was used to seek methodology validation. The results of these four case studies suggest that the methodology is valid, although it is not clear if such production developments would utilize all phases proposed
Mestrado
Explotação
Mestra em Ciências e Engenharia de Petróleo

Since the 1950s, oil has been the dominant source of energy in the world. The cheap supply of oil has been the engine for economic growth in the western world. Since future oil demand is expected to increase, the question to what extent future production will be available is important.

The belief in a soon peak production of oil is fueled by increasing oil prices. However, the reliability of the oil price as a single parameter can be questioned, as earlier times of high prices have occurred without having anything to do with a lack of oil. Instead, giant oil fields, the largest oil fields in the world, can be used as a parameter.

A giant oil field contains at least 500 million barrels of recoverable oil. Only 507, or 1 % of the total number of fields, are giants. Their contribution is striking: over 60 % of the 2005 production and about 65 % of the global ultimate recoverable reserve (URR).

However, giant fields are something of the past since a majority of the largest giant fields are over 50 years old and the discovery trend of less giant fields with smaller volumes is clear. A large number of the largest giant fields are found in the countries surrounding the Persian Gulf.

The domination of giant fields in global oil production confirms a concept where they govern future production. A model, based on past annual production and URR, has been developed to forecast future production from giant fields. The results, in combination with forecasts on new field developments, heavy oil and oil sand, are used to predict future oil production.

In all scenarios, peak oil occurs at about the same time as the giant fields peak. The worst-case scenario sees a peak in 2008 and the best-case scenario, following a 1.4 % demand growth, peaks in 2018.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2015.
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Com a crescente demanda por energia fóssil as operadoras petrolíferas têm buscado determinar planos operacionais que otimizam a produção dos campos em operação para satisfazer a demanda do mercado e reduzir os custos operacionais. Neste contexto, a pesquisa operacional tem se mostrado uma importante ferramenta para determinação dos planos de produção de curto prazo para campos de petróleo complexos. Alguns trabalhos já desenvolveram estratégias para a otimização integrada da produção que visam auxiliar engenheiros de produção e operadores a atingir condições de operação ótimas. Estes avanços científicos atestam o potencial da área de otimização integrada da produção de campos, justificando a busca por estratégias de otimização global e integradas de ativos. Contudo, a incerteza dos parâmetros que caracterizam o reservatório, os poços, fluidos e os diversos processos de produção não vem sendo considerada pelos modelos e algoritmos de otimização da produção diária. Considerando os modelos de produção de curto prazo, estas incertezas podem ser atribuídas a erros de medição , comportamento oscilatório dos sistemas, modelos imprecisos, entre outros. A influência da incerteza dos parâmetros em problemas de otimização tem, desde tempos, sido foco da comunidade de programação matemática. E já foi verificado que soluções de problemas de otimização podem apresentar significativa sensibilidade à pertubações nos parâmetros do dado problema, podendo levar a soluções não factíveis, subótimas ou ambas. Assim, buscando tornar as abordagens de otimização existentes mais confiáveis e robustas às incertezas intrínsecas dos sistemas de produção, esta dissertação investiga a modelagem e tratamento de incertezas na otimização diária da produção e propõe formulações em programação matemática para otimização robusta da produção de poços operados por gas-lift. As formulações representam curvas amostradas através de dados simulados ou medidos que refletem as incertezas dos sistemas de produção. Estas representações levam a formulações robustas em programação matemática inteira mista obtidas pela aproximação das curvas de produção através de linearização por partes. Além disso, este trabalho apresenta os resultados de uma analise computacional comparativa da aplicação da formulação robusta e da formulação nominal a um campo de petróleo em ambiente de simulação, porém considerando simuladores multifásicos amplamente empregados pela indústria do petróleo e gás, que representam a fenomenologia muito próximo da realidade. O primeiro capítulo apresenta a problemática em que estão envolvidos os desenvolvimentos realizados nesta dissertação e um resumo dos capítulos subsequentes. No segundo capítulo alguns conceitos fundamentais são apresentados para a compreensão do trabalho desenvolvido. Este capítulo é dividido em três partes. A primeira parte inicia apresentando brevemente a indústria de petróleo e gás com uma perspectiva histórica, econômica e dos processos envolvidos. Na sequência são expostos conceitos básicos de engenharia de petróleo necessários para o entendimento do sistema de produção utilizado ao longo a dissertação  i.e. gas-lift. Finalmente, o problema de otimização da produção é situado dentro do problema maior, que é o gerenciamento completo das operações de um campo de petróleo, seguido de uma revisão da literatura no que se refere a abordagens clássicas para otimização da produção de campos operados por gas-lift. A segunda parte é uma descrição compacta sobre modelagem de problemas de otimização utilizando programação matemática e na menção dos métodos de solução deste tipo de problema utilizados na parte experimental desta dissertação. A terceira parte começa com uma revisão sobre incerteza em problemas de otimização e sobre as decisões de modelagem enfrentadas quando na presença de problemas de otimização incertos. Na sequência o paradigma de otimização robusta é introduzido e é apresentada uma compilação de alguns dos principais resultados da área de otimização robusta linear. Além disso, ao fim, alguns pontos específicos da teoria de otimização robusta são apresentados pela suas relevâncias para o desenvolvimento da teoria dos capítulos seguintes. O terceiro capítulo inicia com uma discussão sobre as origens das incertezas nos modelos de produção para então prover uma revisão bibliográfica dos poucos trabalhos que mencionam ou lidam com incerteza em sistemas de produção. Na sequência, a incerteza é examinada na perspectiva do problema de otimização. Um sistema simples é usado para exemplificar a metodologia de otimização robusta desenvolvida nesta dissertação. O quarto capítulo apresenta dois problemas padrões de otimização da produção, um contendo poços satélites e outro com poços e completação submarina. Para ambos uma formulação em programação linear inteira mista é descrita considerando valores nominais para todos os parâmetros. Então, para cada problema uma reformulação robusta é implementada considerando incerteza nas curvas de produção do poço. A metodologia utilizada para o primeiro problema é a mesma detalhada no capítulo três, e para o segundo uma extensão da metodologia é proposta para poder lidar com restrições de igualdade incertas. No quinto capítulo são apresentados resultados experimentais de um problema de otimização da produção de um campo com poços satélites. Os resultados obtidos com otimização clássica (nominal) e com otimização robusta são então comparados em um campo de produção sintético instanciado em um simulador multifásico comercial. A solução robusta se mostrou indicada para cenários de operação mais críticos onde factibilidade e segurança são prioridade. No capítulo final uma análise dos resultados obtidos na dissertação é feita sob a perspectiva do possível emprego das técnicas desenvolvidas na indústria de óleo e gás. Apesar de à primeira vista os resultados serem conservadores e de sua utilização parecer limitada, existe potencial para a metodologia ser empregada no caso de situações que priorizam segurança. Além disso a metodologia aqui desenvolvida pode servir como ponto inicial para pesquisas e desenvolvimentos futuros. Uma breve descrição de possíveis trabalhos futuros é feita ao final deste capítulo. O apêndice traz a descrição de algoritmos de amostragem de curvas côncavas desenvolvidos para os experimentos numéricos realizados na dissertação.

Abstract : Managing production of complex oil fields with multiple wells and coupled constraints remains a challenge for oil and gas operators. Some technical works developed strategies for integrated production optimization to assist production engineers in reaching best operating conditions. However, these works have neglected the uncertainties in the well-performance curves and production processes, which may have a significant impact on the operating practices. The uncertainties may be attributed to measurement errors, oscillating behavior, and model inaccuracy, among others. To this end, this dissertation investigates how uncertainty might be considered in daily production optimization and proposes formulations in mathematical programming for robust production optimization of gas-lifted oil fields. The formulations represent system-measured and simulated sample curves that reflect the underlying uncertainties of the production system. The representations lead to robust mixed-integer linear programming formulations obtained from piecewise-linear approximation of the production functions. Further, this work presents results from a computational analysis of the application of the robust and nominal formulations to a representative oil fields available in simulation software.

Production optimization for water flooding in the secondary phase of oil recovery is the main topic in this thesis. The emphasis has been on numerical optimization algorithms, tested on case examples using simple hypothetical oil reservoirs. Gradientbased optimization, which utilizes adjoint-based gradient computation, is used to solve the optimization problems. The first contribution of this thesis is to address output constraint problems. These kinds of constraints are natural in production optimization. Limiting total water production and water cut at producer wells are examples of such constraints. To maintain the feasibility of an optimization solution, a Lagrangian barrier method is proposed to handle the output constraints. This method incorporates the output constraints into the objective function, thus avoiding additional computations for the constraints gradient (Jacobian) which may be detrimental to the efficiency of the adjoint method. The second contribution is the study of the use of second-order adjoint-gradient information for production optimization. In order to speedup convergence rate in the optimization, one usually uses quasi-Newton approaches such as BFGS and SR1 methods. These methods compute an approximation of the inverse of the Hessian matrix given the first-order gradient from the adjoint method. The methods may not give significant speedup if the Hessian is ill-conditioned. We have developed and implemented the Hessian matrix computation using the adjoint method. Due to high computational cost of the Newton method itself, we instead compute the Hessian-timesvector product which is used in a conjugate gradient algorithm. Finally, the last contribution of this thesis is on surrogate optimization for water flooding in the presence of the output constraints. Two kinds of model order reduction techniques are applied to build surrogate models. These are proper orthogonal decomposition (POD) and the discrete empirical interpolation method (DEIM). Optimization using a trust-region framework (TRPOD) is then performed on the surrogate models. Furthermore, the output constraints are again handled by the Lagrangian barrier method

There are many heavy oil reservoirs with thin pay zones (less than 10 m) in the world and in Turkey. Conventional steam injection techniques are not costeffective for such reservoirs, due to excessive heat loss through the overburden. Heat losses can be minimized through controlled heating of the pay zone. One such way is to introduce heat to the reservoir in a controlled manner is microwave heating. Laboratory studies on microwave heating of a scaled model of a heavy oil reservoir with a thin pay zone are presented with an economical feasibility of the method. In this thesis, three different conceptual oil reservoirs from south east Turkey are evaluated: Bati Raman (9.5 API) and Ç
amurlu (12 API) heavy crude oils and paraffinic Garzan (26 API)crude oil. Using a graphite core holder packed with crushed limestone with crude oil and water microwave effects of operational parameters like heating time and waiting period as well as rock and fluid properties like permeability, porosity, wettability, salinity, and initial water saturation are studied. The main recovery mechanisms for the experiments are viscosity reduction and gravity drainage. An analytical model is developed by coupling heat equation with the electromagnetic dissipated power per unit of volume based in Maxwell'
s equation successfully models the experiments for temperatures less than the pyrolysis temperature is presented. Also the experiments are scaled to the model by geometric similarity concept. In economic evaluation, the cost of oil is calculated based on domestic electricity prices.

Thesis (M.S.)--West Virginia University, 2005.
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Current methods of production forecasting such as decline curve analysis (DCA) or numerical simulation require years of historical production data, and their accuracy is limited by the choice of model parameters. Unconventional resources have proven challenging to apply traditional methods of production forecasting because they lack long production histories and have extremely variable model parameters. This research proposes a data-driven alternative to reservoir simulation and production forecasting techniques. We create a proxy-well model for predicting cumulative oil production by selecting statistically significant well completion parameters and reservoir information as independent predictor variables in regression-based models. Then, principal component analysis (PCA) is applied to extract key features of a well’s time-rate production profile and is used to estimate cumulative oil production. The efficacy of models is examined on field data of over 400 wells in the Eagle Ford Shale in South Texas, supplied from an industry database. The results of this study can be used to help oil and gas companies determine the estimated ultimate recovery (EUR) of a well and in turn inform financial and operational decisions based on available production and well completion data.

Most investments in the oil and gas industry involve considerable risk with a wide range of potential outcomes for a particular project. However, many economic evaluations are based on the &ldquo
most likely&rdquo
results of variables that could be expected without sufficient consideration given to other possible outcomes and it is well known that initial estimates of all these variables have uncertainty. The data is usually obtained during drilling of the initial oil well and the sources are geophysical (seismic surveys) for formation depths and areal extent of the reservoir trap, well logs for formation tops and bottoms, formation porosity, water saturation and possible permeable strata, core analysis for porosity and saturation data and DST (Drill-Stem Test) for possible oil production rates and samples for PVT (Pressure Volume Temperature) analysis to obtain FVF (Formation Volume Factor) and others. The question is how certain are the values of these variables and what is the probability of these values to occur in the reservoir to evaluate the possible risks. One of the most highly appreciable applications of the risk assessment is the estimation of volumetric reserves of hydrocarbon reservoirs. Monte Carlo and moment technique consider entire ranges of the variables of Original Oil in Place (OOIP) formula rather than deterministic figures. In the present work, predictions were made about how statistical distribution and descriptive statistics of porosity, thickness, area, water saturation, recovery factor, and oil formation volume factor affect the simulated OOIP values. The current work presents the case of two different oil fields in Turkey. It was found that both techniques produce similar results for 95%. The difference between estimated values increases as the percentages decrease from 50% and 5% probability.

The purpose of the thesis is to study fluid displacement operations in complex pipe geometries utilized in offshore petroleum industry. Typically, MEG or Methanol is circulated through specific sections of the subsea production systems to lower the hydrocarbon content. This is often done at the beginning of production after a prolonged production shut-in, to avoid formation of hydrates or to minimize the emissions of chemicals to the environment. Experimental and numerical analyses have been conducted modifying a previously built pipe system formed a U-shaped jumper, adding a fluid recirculation line, a jet pump, a centrifugal pump, some new valves and sensors. During the experiments the volume fraction in the U-shaped jumper of the displacing fluid was estimated versus time by measuring the level of the oil-water interface in each pipe segment. The system was filled and displaced with both distilled water with 3% water content of salt and Exxsol D60. Numerical simulations were performed using the one-dimensional transient multi-phase flow simulator LedaFlow. It has been investigated the necessary displacing time required to achieve target hydrocarbon concentration in the domain, optimal displacement rate for efficiently removal of hydrocarbons, and how these variables depend on two different fluids (oil and water) and their properties. The displacement has been also modelled including or removing the recirculation line. After carrying out the simulations and performing the experiments, the results were compared, also against a new simplified mathematical model based on uniform mixing in a tank with the same volume as the pipe geometry. The results show that there is a fair agreement between the experimental results, and the results of the simplified model and the LedaFlow simulations. When including the recirculation line it took longer time to reach the target volume fraction, but the displacing rate can be lower than when the recirculation line is not present.

The petroleum industry is currently moving to meet the ever-rising demand for oil and gas production. As onshore fields become depleted and decline in production, exploration and production companies have started venturing further offshore. To support this activity, there is need for new subsea production technologies to develop deepwater and ultra deepwater fields.Woodside Hydrocarbon Research Facility (WHRF) at Curtin University of Technology is working on natural gas dehydration processing using gas hydrate technology. Through the studies, a novel gas dehydration process has been developed and now proposed for subsea application. Natural gas dehydration processes generate both a treated dry gas stream and a waste stream of condensate consisting of both hydrocarbons and water. This condensate can be reinjected to the reservoir formation but this is not always economic or practical. Availability of an alternative means of treatment and disposal of the condensate would be advantageous. This study aims to investigate and to provide a basis for the design of such an alternative scheme by constructing a floating separator for the treatment and disposal of waste condensate from subsea dehydration stage.A model was developed to simulate the process of evaporation of condensate from the proposed floating separator. The calculations were performed taken into account zero wind speed and an ambient temperature around 34 C. The simulation results showed that condensate skimming time was found to be 15 days for flowrate (Qin) of 100 bbd associated with specific separator diameter and total height dimensions. By considering the ratio of diameter to total height of 2.5, the floating separator was designed to enhance the evaporation rate and to get overall structure stability due to the mechanical restrictions that might be encountered in the sea.

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Diversos sistemas existentes, seja na natureza, sejam nas sociedades humanas apresentam acaracterística peculiar de serem formados por subsistemas ou indivíduos que cooperam entre si para a realização de suas tarefas, e consequentemente alcançarem um objetivo global. Exemplos desses sistemas vão de uma sociedade de abelhas a uma organização financeira, de uma comunidade animal a um sistema de manufatura, entre tantos outros. Ao se observar um campo de produção de petróleo, por exemplo, é possível perceber a natureza distribuída e colaborativa desse tipo de sistema, onde diversos poços (de produção ou injeção), estações de coleta e tratamento de óleo, entre outros, distribuídos geograficamente, têm uma distribuição que naturalmente os induziria a cooperar constantemente para que os objetivos de produção sejam atingidos. Apesar disso, as atuais arquiteturas para operação de um campo de produção utilizam uma estrutura centralizada para o seu gerenciamento. As oportunidades advindas da automação, do aumento da capacidade de processamento dos sistemas computacionais e da diminuição do custo das plataformas de hardware têm, por sua vez, ensejado oportunidades para aperfeiçoar o modo de produção dos campos de petróleo. Os sistemas de manufatura por sua vez, têm sido cada vez mais influenciados pelos sistemas multiagentes, um novo paradigma para o desenvolvimento de software que tem no agente o seu elemento principal. Alguns dos benefícios deste paradigma são: maior poder de atuação, por conta comportamento autônomo e inteligente, maior capacidade de lidar com as falhas nos sistemas de computação, por conta da descentralização do controle, e maior flexibilidade por conta da estrutura dinâmica dos agentes. Este trabalho apresenta um modelo baseado em sistema multiagente para o gerenciamento e controle de um campo de petróleo, cuja proposta visa a dotar cada unidade do sistema produtivo com a capacidade de análise local de suas condições baseada no conhecimento especialista embarcado, de comunicação e de negociação com outras unidades a fim de estabelecer decisões com base em uma visão global do sistema que permita consequentemente, melhorar a sua operação.
Salvador

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Produced water is characterized as one of the most common wastes generated during exploration and production of oil. This work aims to develop methodologies based on comparative statistical processes of hydrogeochemical analysis of production zones in order to minimize types of high-cost interventions to perform identification test fluids - TIF. For the study, 27 samples were collected from five different production zones were measured a total of 50 chemical species. After the chemical analysis was applied the statistical data, using the R Statistical Software, version 2.11.1. Statistical analysis was performed in three steps. In the first stage, the objective was to investigate the behavior of chemical species under study in each area of production through the descriptive graphical analysis. The second step was to identify a function that classify production zones from each sample, using discriminant analysis. In the training stage, the rate of correct classification function of discriminant analysis was 85.19%. The next stage of processing of the data used for Principal Component Analysis, by reducing the number of variables obtained from the linear combination of chemical species, try to improve the discriminant function obtained in the second stage and increase the discrimination power of the data, but the result was not satisfactory. In Profile Analysis curves were obtained for each production area, based on the characteristics of the chemical species present in each zone. With this study it was possible to develop a method using hydrochemistry and statistical analysis that can be used to distinguish the water produced in mature fields of oil, so that it is possible to identify the zone of production that is contributing to the excessive elevation of the water volume.
A ?gua produzida caracteriza-se como um dos res?duos mais comuns gerados durante as fases de explora??o e produ??o de petr?leo. Este trabalho tem como objetivo desenvolver metodologias baseadas em processos estat?stico-comparativos de an?lises hidrogeoqu?micas de zonas de produ??o com o objetivo de minimizar tipos de interven??es de altos custos para realiza??o de teste de identifica??o de fluidos TIF. Para o estudo, foram coletadas 27 amostras de cinco zonas de produ??o diferentes e foram medidos um total de 50 esp?cies qu?micas. Ap?s as an?lises qu?micas foi aplicado o tratamento estat?stico aos dados, utilizando o Software Estat?stico R, vers?o 2.11.1. O tratamento estat?stico foi realizado em tr?s etapas. Na primeira etapa, o objetivo foi verificar o comportamento das esp?cies qu?micas em estudo em cada zona de produ??o atrav?s da an?lise gr?fica descritiva. A segunda etapa consistiu em identificar uma fun??o que classificasse as zonas de produ??o de cada amostra, utilizando An?lise Discriminante. Na etapa de treinamento, a taxa de acerto de classifica??o da fun??o da an?lise discriminante foi de 85,19%. A etapa seguinte do tratamento estat?stico dos dados utilizou An?lise de Componentes Principais para, atrav?s da redu??o do n?mero de vari?veis obtidas a partir da combina??o linear das esp?cies qu?micas, tentar melhorar a fun??o discriminante obtida na segunda etapa e aumentar o poder de discrimina??o dos dados, por?m o resultado n?o foi satisfat?rio. Na An?lise de Perfis foram obtidas curvas para cada zona de produ??o, baseadas nas caracter?sticas das esp?cies qu?micas presentes em cada zona. Com este trabalho foi poss?vel desenvolver uma metodologia utilizando a hidroqu?mica e a an?lise estat?stica que pode ser utilizada para distinguir a ?gua produzida em campos maduros de petr?leo, de forma que seja poss?vel identificar a zona de produ??o que est? contribuindo para a eleva??o excessiva do volume de ?gua.

*‘Pasja’ (Brassica campestris x napus) and kale (Brassica oleracea var. acephala L.) were grown at Lincoln, Canterbury, New Zealand in 2008 with different levels of phosphorus (P) fertiliser. Banded or broadcast P fertiliser was applied at 0, 20, 40 and 60 kg P/ha at establishment. Total dry matter (DM) production, the proportion of the leaf and stem and leaf area development were measured over time and related to the biophysical environment. For ‘Pasja’, final DM increased with P rate from 3730 kg DM/ha to ~4900 kg DM/ha at 60 kg P/ha. For kale the increase was from 8710 kg DM/ha for the control to ~11000 kg DM/ha for all P treatments. The leaf to stem ratio declined from 22-31 at 17 days after emergence to 10.4 at the final harvest for ‘Pasja’, which meant the crop was effectively made up mainly of leaf (~90%). The ratio for kale declined from 2.7 at 24 days after emergence to 0.64 at the final harvest. The leaf to stem ratio for both species did not respond to either the method of application or rate of P. Seedling DM accumulation increased with applied P over the first 10 to 17 DAE for ‘Pasja’ and kale respectively. The crops went from shoot growth priority to root growth. The phyllochron of both species was unaffected by P application but responded linearly to the temperature above 0°C. For ‘Pasja’ the phyllochron was 60°Cd compared with 109°Cd for kale. As a consequence ‘Pasja’ developed its canopy and reached critical leaf area index (LAIcrit) earlier than kale. Leaf area index (LAI) for the control crops of both species was lower than for P fertiliser treatments with a maximum of 3.6 for ‘Pasja’ and 3.8 for kale. There was no difference in leaf area indices among the P fertiliser treatments for ‘Pasja’, while kale LAI differed with the rate of P application up to 40 kg P/ha. Total accumulated intercepted solar radiation (RIcum) was 8 and 11% greater for ‘Pasja’ and kale crops respectively when P was applied compared with the control. Thus, the difference in total dry matter yield due to P application was attributed to the difference in RIcum. Neither the method of application or rate of P applied affected the radiation use efficiency (RUE) of either crop. For ‘Pasja’ the RUE was 1.1 g DM/MJ PAR and for kale 1.33 g DM/MJ PAR. Based on this research, it was concluded that P application increased RIcum as a result of increased LAI. The difference in total DM yield was attributed to differences in RIcum. It is recommended that farmers growing ‘Pasja’ and kale under similar conditions to this experiment should apply 40 kg P/ha for ‘Pasja’ and band 20 kg P/ha for kale. *‘Pasja’ is considered both as a species and cultivar in this document as it marketed as such in New Zealand. Technically ‘Pasja’ is a leaf turnip.

This work addresses the poroelastic effect on the processes involved in hydraulic fracturing and post-fracture production using a finite element based fully coupled poroelastic model which includes a triple system of wellbore-fracture-reservoir. A novel numerical procedure for modeling hydraulic fracture propagation in a poroelastic medium is introduced. The model directly takes into account the interaction of wellbore, hydraulic fracture and reservoir in a fully coupled manner. This allows realistic simulation of near fracture phenomena such as back stress and leak-off. In addition, fluid leak-off is numerically modeled based on the concept of fluid flow in porous media using a new technique for evaluating local pressure gradient. Besides, the model is capable of accommodating the zone of reduced pressure (including intermediate and fluid lag zones) at the fracture front so as to capture the behavior of fracture tip region more realistically. A fully coupled poroelastic model for gas reservoirs has been also developed using an innovative numerical technique. From the results of this study it has been found that fracture propagation pressure is higher in poroelastic media compared to that of elastic media. Also high formation permeability (in the direction normal to the hydraulic fracture) and large difference between minimum horizontal stress (in case of it being the smallest principal stress) and reservoir pressure reduce the rate of fracture growth. Besides, high pumping rate is more beneficial in elongating a hydraulic fracture whereas high viscous fracturing fluid is advantageous in widening a hydraulic fracture. It has been also shown that rock deformation, permeability anisotropy and modulus of elasticity can have a significant effect on fluid flow in a hydraulically fractured reservoir. Furthermore, it has been shown that long stress reversal time window and large size of stress reversal region can be caused by high initial pressure differential (i.e. the difference between flowing bottomhole pressure and reservoir pressure), low initial differential stress (i.e. the difference between maximum and minimum horizontal stresses) and low formation permeability in tight gas reservoirs. By taking advantage of production induced change in stress state of a reservoir, this study has also shown that a refracture treatment, if carried out in an optimal time window, can lead to higher economic gain. Besides, analysis of stress reversal region has depicted that a small region with high stress concentration in the vicinity of the wellbore could impede refracture from initiating at the desired place. Moreover, re-pressurization of the wellbore can result in further propagation of the initial fracture before initiation or during propagation of the secondary fracture.

Alkaline/surfactant/polymer (ASP) flooding is of increasing interest and importance because of high oil prices and the need to increase oil production. The benefits of combining alkali with surfactant are well established. The alkali has very important benefits such as lowering interfacial tension and reducing adsorption of anionic surfactants that decrease costs and make ASP a very attractive enhanced oil recovery method provided the consumption is not too large and the alkali can be propagated at the same rate as a synthetic surfactant and polymer. However, the process is complex so it is important that new candidates for ASP be selected taking into account the numerous chemical reactions that occur in the reservoir. The reaction of acid and alkali to generate soap and its subsequent effect on phase behavior is the most crucial for crude oils containing naphthenic acids. Using numerical models, the process can be designed and optimized to ensure the proper propagation of alkali and effective soap and surfactant concentrations to promote low interfacial tension and a favorable salinity gradient. The first step in this investigation was to determine what geochemical reactions have the most impact on ASP flooding under different reservoir conditions and to quantify the consumption of alkali by different mechanisms. We describe the ASP module of UTCHEM simulator with particular attention to phase behavior and the effect of soap on optimum salinity and solubilization ratio. Several phase behavior measurements for a variety of surfactant formulations and crude oils were successfully modeled. The phase behavior results for sodium carbonate, blends of surfactants with an acidic crude oil followed the conventional Winsor phase transition with significant three-phase regions even at low surfactant concentrations. The solubilization data at different oil concentrations were successfully modeled using Hand's rule. Optimum salinity and solubilization ratio were correlated with soap mole fractions using mixing rules. New ASP corefloods were successfully modeled taking into account the aqueous reactions, alkali/rock interactions, and the phase behavior of soap and surfactant. These corefloods were performed in different sandstone cores with several chemical formulations, crude oils with a wide range of acid numbers, brine with a wide range of salinities, and a wide range of temperatures. 2D and 3D sector model ASP simulations were performed based on field data and design parameters obtained from coreflood history matches. The phenomena modeled included aqueous phase chemical reactions of the alkaline agent and consequent consumption of alkali, the in-situ generation of surfactant by reaction with the acid in the crude, surfactant/soap phase behavior, reduction of surfactant adsorption at high pH, cation exchange with clay, and the effect of co-solvent on phase behavior. Sensitivity simulations on chemical design parameters such as mass of surfactant and uncertain reservoir parameters such as kv/kh ratio were performed to provide insight as the importance of each of these variables in chemical oil recovery. Simulations with different permeability realizations provided the range for chemical oil recoveries. This study showed that it is very important to model both surface active components and their effect on phase behavior when doing mechanistic ASP simulations. The reactions between the alkali and the minerals in the formation depend very much on which alkali is used, the minerals in the formation, and the temperature. This research helped us increase our understanding on the process of ASP flooding. In general, these mechanistic simulations gave insights into the propagation of alkali, soap, and surfactant in the core and aid in future coreflood and field scale ASP designs.
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The large volume of water produced during the extraction of oil presents a significant problem due to the high cost of disposal in an environmentally friendly manner. On average, an estimated seven barrels of water is produced per barrel of oil in the US alone and the associated treatment and disposal cost is an estimated $5-10 billion. Besides making oil-water separation more complex, produced water also causes problems such as corrosion in the wellbore, decline in production rate and ultimate recovery of hydrocarbons and premature well or field abandonment. Water production can be more problematic during waterflooding in a highly heterogeneous reservoir with vertical communication between layers leading to unevenness in the flood front, cross-flow between high and low permeability layers and early water breakthrough from high permeability layers. Some of the different technologies that can be used to counteract this involve reducing the mobility of water or using a permeability block in the higher permeability, swept zones. This research was initiated to evaluate the potential effectiveness of the latter method, known as deep diverting gels (DDG) to plug thief zones deep within the reservoir and far from the injection well. To evaluate the performance of DDG, its injection was modeled, sensitivities run for a range of reservoir characteristics and conditions and an economic analysis was also performed. The performance of the DDG was then compared to other recovery methods, specifically waterflooding and polymer flooding from a technical and economic perspective. A literature review was performed on the background of injection profile control methods, their respective designs and technical capabilities. For the methods selected, Schlumberger's Eclipse software was used to simulate their behavior in a reservoir using realistic and simplified assumptions of reservoir characteristics and fluid properties. The simulation results obtained were then used to carry out economic analyses upon which conclusions and recommendations are based. These results show that the factor with the largest impact on the economic success of this method versus a polymer flood was the amount of incremental oil produced. By comparing net present values of the different methods, it was found that the polymer flood was the most successful with the highest NPV for each configuration followed by DDG.

In this experiment, the effects of (1) lipid type (soy bean oil, tallow and fish oil), (2) the period the fish oil was provided and (3) a dietary supplement containing conjugated linoleic acid (CLA), selenium (Se), vitamin E and vitamin C on pig performance and pork quality were studied. Forty-eight female pigs (PIC hybrids, with a mean live weight of 16.19 kg ± 1.56 SD) were obtained from a single commercial operation in the North Island of New Zealand. The pigs were rank ordered by weight and assigned to one of six dietary treatment groups. The diet base was either a combination of animal and plant feedstuffs (AT and PTS), plant feedstuffs only (PO, POS) or plant feedstuffs combined with fish oil (PFSe and PFSl). The diets also differed depending on the presence or absence of the nutritional supplement SanoviteTM and a vitamin C supplement. SanoviteTM is a trademarked dietary supplement containing CLA (BASF, Auckland, New Zealand), organic Selenium (Alltech Inc., Nicholasville, KY) and vitamin E (Morel et al., 2008). Diets POS, PTS, PFSe, PFSl contained SanoviteTM and a vitamin C supplement. Diets PO and POS were used to establish the effect of the supplementation with SanoviteTM and the vitamin C supplement. Pigs fed diet PFSe received plant feedstuffs and fish oil with supplement between days 1 and 35 and then diet POS up to day 84. Pigs fed diet PFSl received diet POS between days 1 and 35; plant feedstuffs and fish oil with supplement between days 36 and 56 and then diet POS up to day 84. Pigs in group PFSe and PFSl both received the same total amount of fish oil per pig (2.52 l/ 2.31 kg). Between days 1 and 56 of the experiment grower diets were fed, and finisher diets were fed between days 57 and 84 of the experiment. The pigs were kept in pens of six, but fed individually twice daily (at approximately 8 am and 3.30 pm) according to a fixed feeding schedule. Water was available at all times. Individual feed intakes were measured daily and live weight recorded weekly. Faeces were collected once a day during two days in week five of the trail for digestibility determination. Carcass quality characteristics determined at the abattoir included carcass weight and back fat thickness as measured at the end of the slaughter line. Meat quality assessments were performed on the Semimembranosus muscle (SM) from one of the topside cuts of each pig. Measurements of fatty acid profile (loin and backfat) and the Se content (lean meat) were conducted in Singapore by Mrs. J. Leong (MSc). In this study plant or animal feedstuffs, lipid type, SanoviteTM and vitamin C supplementation had no significant effects on growth performance and carcass quality. There were no differences in apparent faecal digestibility characteristics for dry matter (DDM) and organic matter (DOM) in the un-supplemented animal (AT) and plant based (PO) diets. Lipid type had a significant effect on the digestibility of ash (DA), and an increased ratio of unsaturated fatty acid to saturated fatty acid resulted in increases in DDM and DOM. DDM and DOM increased when soybean and linseed oil (POS) were used instead of tallow (PTS) or fish oil (PFS). The main differences in DDM, DOM and DA were observed between diets PO and POS. A positive effect of selenium, vitamin E and CLA supplementation is suggested. Increased cooking temperatures reduced tenderness (higher mean, peak force, yield force and peak force – yield force) and increased cooking loss. There was a significant negative relationship between ultimate pH and relative lightness (L*). There were highly significant positive correlations between all three measurements of expressed juice, and there was a significant positive correlation between cooking loss at 60 and 70oC (P<0.01) but correlations between expressed juice values and cooking loss were not significant. The P-values for the contrasts for cooking loss at 70 0C were significant for all contrasts except for AT vs PO and PFSe vs PFSl. For all other contrasts, the P-values for cooking loss at 70 0C were significantly higher in group POS than for groups PO, PTS and PFSe+PFSl. The P-value for (Peak force – Yield force) at 70°C was significantly higher in samples from group PFSe than for samples from group PFSl. The P-value for the myofibrillar fragmentation index (MFI) was significantly higher for group AT in contrast to group PO. Group POS had a significantly higher P-value for MFI in contrast to groups PO, PTS and PFSe and PFSl. Group POS had a lower P-value for sarcomere length in contrast to groups PFSe and PFSl. Group PFSe had a significantly higher P-value for sarcomere length in contrast to group PFSl. Group PFSe had a significantly higher P-value for expressed juice percentage loss in weight in contrast to group PFSl. Supplementing with SanoviteTM increased the Se content (P = 0.002) in lean meat as analysed by J. Leong (2010, personal communication). In general it was concluded that an increase in the ratio of unsaturated fatty acid to saturated fatty acid (U/S) in the diet resulted in higher levels of unsaturated fatty acids in loin and backfat. The fatty acid profile in the diet reflected the fatty acid profile of pork. Backfat of pigs fed diets including soybean and linseed oil contained higher levels of linoleic and α-linolenic acids. Diets PO and POS were used to establish the effect of the supplementation of CLA. The backfat of pigs fed diet POS contained higher levels of CLA (C18:2-trans-10, cis-12) and α-linolenic acid than pigs fed diet PO. The loin of pigs fed diet POS contained higher levels of palmitoleic and linoleic acid and CLA (C18:2-cis-9, trans-11) and lower levels of oleic acid than pigs fed diet PO. The use of fish-oil as a lipid type resulted in the highest levels of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) in loin and backfat. The loin and backfat of pigs fed fish-oil in the second part of the grower phase (PFSl) contained higher levels of EPA, DPA and DHA than pigs fed fish-oil in the first part of the grower phase (PFSe). By enriching the swine diet with long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) it was possible to increase the EPA, DPA and DHA content of pork. Enriching pork with LC n-3 PUFA will contribute to achieving standards for adequate intake (AI), but might not be suitable to reach suggested dietary targets (SDT). In conclusion, it was possible to change the pork composition by dietary manipulation without compromising pig performance and meat quality. There were a few significant effects from treatments on meat quality characteristics, but differences reported in this study were small and relatively unimportant. A negative influence of the dietary regime on palatability and meat processing was expected, but these issues are beyond the scope of this experiment.

This study investigated methods to reduce herbicide application through improved targeting of weeds, thereby also reducing damage to pastures. The focus was to evaluate and improve wiper and spot-spraying application techniques for pasture herbicides as they reduce chemical use by treating just the weed. Wiper application of herbicides was shown to be a useful technique for controlling Californian thistles. In one trial, a stem reduction of over 90% when assessed 10 months post application was achieved with a double pass of clopyralid, metsulfuron and glyphosate when the plants were treated at the post-flowering stage and were vigorously growing. A double pass was superior to a single pass for glyphosate and triclopyr/picloram, but not for clopyralid and metsulfuron. Subsequent trials produced poor results possibly because of the stressed condition of the thistles and their growth stage as well as lack of consistency in wiper output and operator differences. Despite wiper applicators usually being selective, some damage to pastures was observed in the field, and from a series of experiments it was concluded that rain falling soon after wiper application was the likely cause of pasture damage. An innovative and highly sensitive technique using a spectrophotometer was developed to measure herbicide output from wiper applicators. A spectrophotometer could accurately measure clopyralid concentrations as low as 0.02 g active ingredient in a litre of water. The Eliminator and Rotowiper outputs were found to be highly variable while the Weedswiper was more consistent although it applied less herbicide than the other two wipers. Spot spraying experiments confirmed that glyphosate and metsulfuron create bare patches by damaging both grass and clover while clopyralid and triclopyr/picloram only eliminate clover. However, metsulfuron patches stayed bare for much longer while glyphosate ones quickly filled up with weeds and clover. Ingress of clover stolons appeared to be more important than re-establishment from seed in the recovery of patches. The bigger the damaged patch, the higher the likelihood of recolonisation by opportunistic weeds. Bioassay studies found that over-application of clopyralid and triclopyr/picloram provided residual activity up to 18 and 30 weeks, respectively, thereby potentially preventing re-establishment of white clover. The negative effects on clover seedlings from metsulfuron ranged from 3 to 6 weeks for standard and high rates, respectively, with a stimulatory effect on seedlings thereafter for up to 18 weeks. Dose-response curves for the application of metsulfuron and triclopyr/picloram into the centre 5% versus full plant coverage of Scotch thistle and ragwort rosettes showed that application of herbicide to the centre 5% was as effective at the same concentration and greatly reduced the risk of damage to pasture.