Ensuring a pilot project a success operationally, while gathering reliable data for a full-field implementation is critical. For this reason, various aspects of project planning and operational considerations need to be addressed. This include conceptual design, facilities and operational considerations, resources planning, integration of activities and most importantly, pilot objectives. However, all these planning will not be successful without a properly designed and executed laboratory test program. Such laboratory program will minimize result uncertainty and ensure the proposed pilot meet its objectives. The first Chemical EOR (CEOR) pilot project in Malaysia involved an Alkaline-Surfactant injection utilizing high salinity injection water in a high temperature reservoir. It pioneered the Single Well Chemical Tracer (SWCT) method for EOR project evaluation in Malaysia. The main objective of the pilot is to assess the effectiveness of the Alkaline-Surfactant formulation to improve oil ultimate recovery through the reduction of residual oil saturation. Being the first of its kind in Malaysia, an extensive laboratory program is required to ensure the injected alkaline surfactant formulation performed at its most optimum and conclusive data is gathered. This data will be used as input to the future field development plan. This paper presents a comprehensive laboratory test program covering pre-pilot, pilot and post-pilot laboratory analysis designed for offshore high salinity injection water and high temperature reservoir. It highlights the challenges imposed by offshore operation to design an optimum chemical solution considering that salinity and hardness of the water used to dissolve the chemicals are critical for an alkaline-surfactant system. It also discusses the continuous and controlled quality check process to validate the performance of the alkaline-surfactant solution. Finally, it presents the chemical adsorption study to evaluate chemical flood potential for the future full field CEOR implementation. Introduction PETRONAS has undertaken a 3-year R&D project which evaluated the feasibility of a CEOR process for Malaysian oilfields. The research also identified suitable chemicals that can withstand the high temperature and high salinity environment and suitable candidate reservoir for pilot implementation (Othman et al. 2007). Based on the R&D study, Angsi field, located east coast of Peninsular Malaysia was selected for pilot implementation. The execution of this pilot project was also targeted to establish the required technical, operational and management skills before embarking on a large scale full field chemical flood. The results of the CEOR pilot project are crucial to the future decision making for full field implementation. A lot of considerations were given to gather reliable and conclusive data, within which, will manage results uncertainty. One of the ways is to ensure accuracy of the chemical preparation and injection process. All these can be achieved by a properly designed laboratory test program to tackle specific issues on optimum chemical slug design and quality of chemicals injected. It also aimed to measure the degree of chemical loss to reservoir rock, in which will evaluate the sustainability of the chemicals in a high temperature reservoir.
Foam Assisted Water-Alternating-Gas (FAWAG) flooding is one of the enhanced oil recovery (EOR) technique that had been explored and studied worldwide. The ability of foam to lower the gravity override and create a macroscopic sweeping of oil in the reservoir shows its potential to be a successful technique. However, the rapid degradation of foam at high temperature condition in the presence of light crude oil limits its application. Therefore, introduction of an additive to the surfactant is crucial to maintain foam stability. Nano-scale particle is a well-known material that has attracted a lot of attention due to its unique physiochemical properties. This high surface energy particle has shown to exhibit a catalytic behaviour in various application including EOR chemical flooding. In this study, the effect of four different types of nanoparticles, SiO2 (hydrophilic), SiO2 (hydrophobic), ZnO and TiO2 nanoparticles on foam stability under high temperature condition, and in the presence of light crude oil were investigated. Results from this study has shown that SiO2 nanoparticles of the hydrophilic type at concentration three times lower than the surfactant concentration have significantly improved the foam half-life by 2 times longer than the surfactant alone at temperature of 110°C, in the presence of light crude oil (45° API). No improvement of foam half-life was shown by ZnO nanoparticle used in the surfactant formulation. The presence of SiO2 (hydrophilic) nanoparticles have significantly reduced the detrimental effects of light crude oil and strengthen the foam by increasing the viscosity of surfactant from 4.38 cP to 10.01 cP in the presence of 0.15 wt% SiO2 (philic) nanoparticle. The significant increment in viscosity has maintained the wetness of foam, thus reducing the rate of liquid drainage at the temperature above boiling point of water. The SiO2 (hydrophilic) nanoparticle-surfactant formulation was observed to have produced uniform sized bubbles compared to surfactant formulation alone. This indicates that nanoparticles are able to restrict shrinkage or expansion of bubble by creating a steric layer at the lamella structure which consequently restores the foam stability. The foam stability tests, determined as foam-half-life, were performed using inert nitrogen gas as the gas phase to eliminate other factors that may affect foam stability.
Managing reservoir souring is on of the challenge in oil and gas industry, especially fields without previous records of H2S productions. Due to activities such as waterflooding, reservoirs’ conditions were changed, which indirectly inducing the environment to start producing H2S gas. In low temperature fields, main contributor to the H2S production was identified as biogenic process, where microorganisms catalyzed the sour gas production. Conventionally, sulphate reducing microorganism was always blamed as the culprit in contributing towards H2S production. However, abundance of literatures discussed about contribution of other microorganisms towards souring processes. Due to the complexity of their interactions, current approach to treat or control biogenic souring became one of the most challenging issues. This study will focus on the laboratory studies of sulphide production by microorganisms and modelling various microorganisms interactions towards chemical treatment introduced to mitigate it. Started with microorganisms sampling from fields with high SRB, the samples were then enriched in the laboratory. To identify microorganismss from samples, cultures were sent for PCR and DNA sequencing. Based on the results, microorganisms were profiled. Batch test were conducted by dosing pre-determined dosage of biocide and nitrate. Production of sulphide were monitored up to 92days. Based on the sulphide production, effectiveness of the treatments were determined. A model, which previously developed to determine the potential of reservoir souring, enhanced with addition of dynamic interaction of microorganisms. Factors such as nutrients, type of microorganisms, treatment chemicals, and their byproducts contributed towards the model. microorganisms. In the batch test, chemicals were dosed once into culture. Results obtained shows that nitrate treatment suppressed the sulphide production for ashort term period, where after the nitrate depleted, the number of microorganisms and sulphide productions were bounced back. Biocidetreatment, in contrast, generally suppressed all microorganisms in the cultures, effectively control the microorganisms number and maintaining low sulphide production for the entire duration of the experiment. The model that being developed in this study tested with synthetic data that mimick to field conditions, type of microorganisms and chemical treatments to observe their output pattern. It was found that the pattern output from the synthetic data matched with experimental results, which shows the model was sensitive and reliable to model the mitigation and control strategy for biogenic reservoir souring. The model based on dynamic interactions of microorganisms towards chemical treatments (biocide and/or nitrate) is the novel element in this study. Past studies were always focus on single population model, which SRB is the main input for the model, while this study enhanced its accuracy by introducing multi-population factor.
Angsi field is located offshore Terengganu, Malaysia. It was identified as the candidate for a pilot project to evaluate the effectiveness of chemical enhanced oil recovery (CEOR). Injection of alkali-surfactant (AS) slug was used to improve recovery factor through the reduction of residual oil saturation (Sor). The pilot project utilized single well chemical tracer test technique (SWCTT) to measure Sor change near well bore due to reactions of CEOR process. The pilot results were later used to update the reservoir dynamic model and to support decision making for potential expanded field application. The pilot project faced many challenging technical and operational obstacles: offshore location, high reservoir temperature, sea water as injection water, water softening facilities requirement, and unmanned satellite platform with limited space. In addition, compliance to all Health, Safety, and Environment (HSE) requirements is a must, to ensure the pilot operation is carried out in a safe manner. This paper will focus on the overall pilot design, planning and some results. Operational, HSE and quality control will also be discussed as background to the pilot project.
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