Sustained casing pressure (SCP) is a very costly event for any operator either at production phase or at the end of a well’s lifecycle. SCP is a result of incomplete hydraulic isolation across hydrocarbon bearing zone. In one of the gas fields in Malaysia, notoriously known for shallow gas hazard, drilled development wells which have reportedly been suffering SCP. In the past, various improvements in cement slurry design and placement methods were deployed in order to provide complete zonal isolation, especially at the shallow gas sand, yet SCP issue was encountered occasionally. In the current development campaign, different strategy to providing annulus sealing was adopted. This paper discusses proactive steps taken in the slurry design, fit together with the dual stage cementing approach, as a primary means of placing cement above the shallow hazard interval. During the design phase, essential key parameters that would lead to successful placement of cement in the annulus as well as unique slurry design that suits for two stage cementing methods were studied. Risk involved in first stage cementing is one of the most important steps that should be analyzed in detail and put mitigation measures in place to ensure the second stage cement job can be performed as planned. In addition to the slurry properties, such as fluid-loss value, gas-tightness, etc., thickening time and top of cement (TOC) of the lead slurry in the first stage cement job has become enormously critical in designing dual stage cementing job in order to assure cement ports in the stage collar are not covered with hard cement forcing the termination of second stage job prematurely. Besides cementing design, careful selection of the stage collar location and casing annulus packer in the string is also of significant importance in leading to successful two stage cement job. Two development wells with above approached has been delivered and no sustained casing pressure has been experienced. This proactive approach to use two stage cementing as primary plan has proven to successfully eliminate the risk of SCP, which was a frequent struggle in their sister wells drilled with primary cementing in the past in the same field. The risk analysis combined with careful considerations of critical cementing design parameters and selection of stage tool location have become a novel approach to combat against SCP in this gas field.

The objective of this paper is to share the Operator's first experience in utilizing ilmenite in an offshore HPHT well as part of a low cost well initiative and the value obtained by utilization of such a weighting agent in particular towards lowering ECD. After extensive testing micronized ilmenite was used as the weighting agent for the synthetic based drilling fluid (SBM) for the B1 well. This well was classified as high complexity with a narrow margin window and with predicted maximum bottom hole pressure of 12,013 psi at 3,990 m TVDDF. Extensive laboratory testing was conducted to determine the optimum formulation for a 16 ppg SBM. Part of the methodology in the testing was conducting rheology comparisons between various weighting agents, manganese tetraoxide, barite and micronized ilmenite. The subsequent results were then run through hydraulics simulations to determine the best formulation for optimized hydraulics. Additional testing was conducted to determine the overall stability of the system including conducting static sag tests with a similar duration to the planned wireline logging operation. The primary drivers for using this fluid were to reduce ECD in a narrow margin environment and facilitate the taking of good wireline logs by providing optimum hole conditions without any sag. The micronized ilmenite system successfully achieved a similar rheology to manganese tetraoxide with low PV's of less than 50 cP at 17 ppg and a sag index of less than 0.52. These properties were at an OWR of 80:20. This led to both the successful drilling of the well and completing the required wireline logging with no fluids related NPT or issues related to sag. During logging, the mud was static for 5 days without problems. The mud weight of 17 ppg was the highest density, at that time, at which the micronized ilmenite system had been used.