Estimation of compaction and subsidence is one critical information for designing offshore platform to develop large carbonate gas reservoir. Coupled simulation between reservoir dynamic and geomechanical response is one of well-known approaches to predict the episodic compaction and subsidence through the field life. In this area, reservoir simulation was constructed base on available reservoir information, fluid characteristic and most likely number of wells in the development scenario. The 1D Mechanical Earth Model (MEM) was constructed and used as reference for mechanical properties. As this is an exploration well, mechanical properties such as Young's modulus and pore collapse pressure from nearby fields in the same region were used as a reference. The base case of the coupling simulation shows surface subsidence in a range of 2 meters without consideration of rapid deformation of rock due to pore collapse. This will impact on how the platform will be designed to account for the amount of subsidence throughout 20 years of production. Due to the uncertainty in lacking of key input parameters in the modeling, the uncertainty analysis was performed to assess the impact of each mechanical property on the magnitude of the reservoir compaction and subsidence. In this study, uncertainty analysis were captured results will be presented and discussed. Wide range of surface subsidence can be varied from 2 meters up to 10 meters. This leads to additional acquisition and coring program to narrow down those uncertainty parameters which currently not available in the field.
Recent discovery of huge carbonate reservoir was reported as one of top ten largest discovery in 2019. However, one of the well-known issues in this region is the reservoir compaction and surface subsidence due to the nature of the reservoir characteristic which is highly porous carbonate reservoir. Based on literature review, it was observed that some of the fields in the region were encountered comparatively high subsidence especially the fields that composed of porous mouldic limestones. F23, located in the western part Central Luconia, offshore Sarawak. This field and encounter 4 meters of subsidence as reported from GPS data (Dudley et al., 2007). Subsidence rate for M3 field was reported with 3 meters (Mah and Draup, 2004). When severe surface subsidence occur, it can cause many issues to the field. Facility design need to be changed and remedial action on the platform and facility lift up might be required. Those thing lead to facility shutdown, cost impact, and eventually lost in production and reserves. However, not all carbonate reservoir has the behavior of severe compaction and also it does not occur in all porosity range reservoir. Various concerns related to risks and severity has been raised. This study was designed to provide an answer related to those geomechanics related risks.
