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.
Operators are faced with never-ending well integrity issues relating to tubing leaks. This situation is particularly important in oil and gas wells that are producing in corrosive environments. When a well can no longer be safely produced due to well integrity issues relating to tubing leaks, an expensive workover is often performed to restore the tubing integrity. To improve the economics of a well intervention involving tubing leak repairs, a new cost-effective method is being proposed. The novel technology involves the installation of reinforced thermoplastic pipe (RTP) inside the existing tubing to isolate multiple leaks using a coiled tubing unit or an E-line. The RTP is engineered for downhole applications with custom designed connectors and accessories. It is designed to handle corrosive fluids (CO2 and H2S) and prevent downhole erosion caused by sand production. The RTP can be used to eliminate tubing – annulus communication in both producers and injectors with full compliance to well integrity management system. The results of the field trial in a gas injector well in Malaysia basin show that the RTP can provide a reliable means of restoring and enhancing the production of oil and gas with considerable cost savings (up to 80% cost reduction when compared to a conventional workover). In most cases, the high cost associated with a conventional workover can make it uneconomical when compared to the expected hydrocarbon recovery from the well, resulting in production deferment (well shut-in). The RTP can significantly increase the viability of repairing a larger percentage of the wells that are shut-in due to the loss of tubing integrity when the hydrocarbon recovery from the well is insufficient to justify a full workover. The significant cost savings provided by the RTP would dramatically improve economics and would likely result in more reserves recovered. The RTP also has a smoother surface that contributes to minimum friction and reduces the risk of scales formation when compared to the steel tubing of the same internal diameter.
Microbiologically-induced corrosion (MIC) is an ubiquitous problem in the oil and gas industry. According to NACE, it constitutes 20 percent of the total corrosion cost. PETRONAS itself has to spend RM7.5 million annually to mitigate MIC. This is because if not properly mitigated, MIC could undermine the integrity of the assets, thus posing risks to the operation. One way of mitigating MIC is through the injection of biocide. However, a current commercially available biocide used to control MIC is more effective towards planktonic bacteria; it may take a much higher dosage to be effective on sessile bacteria as they thrive under biofilms that provide nutrients and protection. Realizing this shortcoming, PETRONAS has developed an additive that would improve the efficacy of the biocide by undermining the biofilms. Field testing on two crude oil pipelines has indicated that the addition of the additives allows the biocide to work at 30 percent lower dosage as effectively as the currently recommended dosage in achieving the target bacteria population. This will translate into a considerable saving to PETRONAS, particularly when the price of the biocide has almost doubled.
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