CRACKING NEW CBM POTENTIAL IN SOUTH SUMATERA: CURRENT PROGRESS, OBSTACLES, AND OPPORTUNITIES

摘要

The Coalbed Methane (CBM) development in South Sumatera started with an exploration project of four exploration wells, which were drilled, cored, and analyzed to determine the gas content and the adsorption-desorption curve to estimate the production performance. Based on the analysis, and the production and surface considerations, two wells were forwarded to the dewatering stage: Well X-2 and Well X-3. Both were completed with a pre- perforated casing liner. Well X-2 produced from three seams, while Well X-3 only produced from one coal seam. At the dewatering stage, which is currently being performed, Well X-2 is producing 3.5 MSCFD and 1,800 BWPD. The pressure survey indicated a decline during the first four months, creating a linear trendline toward the Critical Desorption Pressure (CDP). However, the decline was monitored recently as stable during the rainy season, and the water and gas rates also stabilized. This phenomenon raised many issues: does the changing season affect the fluid production? If it does, could this mean there is a recharging process? Based on the isotherm curve, the pressure has not reached the CDP but the gas has already been produced; therefore, could the CDP be regarded as an area of desorption instead of a point? The production from Well X-3 was terminated due to low influx production. Based on the seismic analysis, Well X-3 is located in an area of faults. Does this affect the instability of the coal seam? The source of the water-bearing coal seam in Well X-2 needs to be determined; this could be achieved by undertaking an ion analysis of the water produced. If the water comes from the coal seam, the dewatering process could be improved by drilling four dewatering wells around Well X-2 to create a five-spot producing pattern. However, if it comes from the coal seam as a recharging process, then isolating the water-bearing coal seam needs to be done. The solution for the Well X-3 problem is technically the same; to isolate and open another potential coal seam. Yet, this option is not going to be easy since the completion is open hole. To study the effect of other completion methods, Well X-4 will be completed with a casing to determine which method is suitable for South Sumatera. Although it is still too early to evaluate, as there is still a lack of data and studies, the CBM operations are striving to reach their full potential for their dewatering phase to be considered as an alternative energy for conventional gas and to contribute to additional gas production. Considering the difficulty of land clearance and well site construction for the further development stage involving well numbers in particular, a cluster system development to minimize the footprint will be considered.