Tiung Biru field is a promising development field in East Java, It yielded many discoveries including the Kujung Reservoir containing both gas and oil zones. The operator is only focusing on producing oil zones thus requiring a good annular zonal isolation quality to be able to produce the oil zones without producing the gas zones. Once well construction was finished the cement bond quality behind casing appeared to be mediocre which was compromising the operator production objectives for a number of oil producing zones.Two producing wells in Tiung Biru (TBR) field which produced from Kujung Reservoir were inefficient because of a significant increase of gas production cross flow. A CBL showing high amplitude across the production zone is a strong indication there is communication between a gass bearing zone adjacent to the oil producing interval. Therefore, squeeze cementing was proposed. The success criterion for the squeeze job is the reduction of the GOR (gas oil ratio) by isolating the gas zone from the oil interval close by. The first squeeze cementing attempt was performed with a conventional cement slurry; post job logs showing mediocre cement quality log result and the squeeze was unable to isolate the cross flow. Conventional cement will hydrate and bridge off before it can achieve objective. This paper explains a solution for improving zonal isolation with an engineered and optimized microcement slurry with low fluid loss control, thin filter cake, low rheology resulting in a better stability and performance for the squeeze application. This paper also presents slurry design, execution procedure, pre and post job evaluation.On the execution, slurry can go through the narrow gap behind the casing and improve zonal isolation with evidence of perfect post cement log quality. The slurry penetrated the narrow gaps without dehydrating, and showing good mechanical properties with short setting times (Moulin et al, 1997) which is of prime importance to seal off gas zone and meet isolation objectives. Production test after squeeze also shows that the GOR had reduced drastically.
Emerging technologies, stringent permanent well abandonment regulations, and increasing well complexity affect the way we execute well intervention operations. One of the major operators in the Netherlands had an objective to set underbalanced cement plugs in brine across a deviated section using managed-pressure equipment to overcome high reservoir bottomhole pressure. The project involved several challenges: large-diameter production casing with a requirement to maintain high shut-in wellhead pressure, complex wellbore geometry, operations from a workover rig with zero discharge allowance, corrosive salt environment, and small cement slurry volume. These challenges had to be addressed to complete well abandonment to minimize safety risks, maximize efficiency, and achieve compliance with industry standards and regulatory requirements. This paper discusses two case studies involving underbalanced pump-and-pull and conventional balanced plug placement techniques. Thorough analysis and risk assessment, engineering design approach, comprehensive laboratory testing, and fit-for-purpose surface equipment and downhole tools enabled flawless job execution and placement and achievement of long-term zonal isolation. The first well-barrier elements were successfully verified by tagging and pressure testing in both cases. Results of this study include the following observations and conclusions: Managed-pressure cementing was proven to be an ideal solution for a well abandonment in a reservoir environment of high bottomhole pressure.Highly magnesium-resistant cement slurry design should be considered when setting cement plugs across an extremely corrosive salt environment.Successful verification of the first well-barrier element simplifies operations for subsequent cement plugs. Cost-effective solutions for permanent well abandonment under challenging downhole conditions attracts increasing interest from petroleum engineers due to increasing well complexity and low oil prices that challenge the economics of wells, leading to abandonment. The current paper describes the challenging conditions under which the wells had to be abandoned, thorough analysis of the risks involved, and an effective solution. The design strategy, execution, evaluation, and results for these two wells are discussed in detail and will help to guide success and solve problems related to permanent well abandonment under similar challenging conditions.
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