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.