oa Structural Style and Hydrocarbon Potential of the Dent Peninsula, Eastern Sabah

The eastern Sabah area has undergone several deformational phases. The latest is the Pliocene-Pleistocene deformation, with the maximum stress in NNW direction. This deformation was responsible for shaping the present day landscape of eastern Sabah and also responsible for reactivation of old structures and the formation of latest structures that exist today. In the offshore area, the structures that have been drilled for hydrocarbon are mostly faulted anticlines formed by a combination of wrenching and syn-sedimentary growth-faulting. The hydrocarbon has been discovered in middle to upper Miocene sand, which is equivalent to the onshore SegamalTanjong formations and the Dent Group. This indicates the existence of an active petroleum system is operating in the area. This is also corroborated by the presences of hydrocarbon seeps in the onshore area. The similar structural style is also observed in the onshore eastern Sabah. From structural interpretation of SAR images, it is found that the area is dominated by strike-slip regional faults trending in NE-SW, NW-SE and NNW-SSE. The observed structural grains along the faults indicate wrench movement, which may favor the formation of hydrocarbon traps. There are several types of structures associated with these faults, that are of interest to petroleum exploration such as en echelon drag folds and fault bounded anticlines. Most of these wrench related structures and a few others are common in this area. The outcrops of the Dent Peninsula, eastern Sabah is the uplifted portion of the strata forming the Sandakan sub-basin, which collectively known as the Dent Group. It comprises the Sebahat, Ganduman and Togopi formations, which ranges from middle Miocene to Pleistocene. The succession has been interpreted as a prograding delta, with the Sebahat being the prodelta and marine facies, overlain by the coastal and deltaic Ganduman formation forming the top-set. The Togopi is unconformable upon the underlying formations, marking a major tectonic event in the Late Miocene to Pliocene. The unconformity below the Togopi formation has been interpreted as a major sequence boundary in eastern Sabah. It has been a significant sealing layer for hydrocarbon in the offshore area, where most of the discovered hydrocarbon is trapped by this unconformity. Since its coverage extend into the onshore area, it is possible to find hydrocarbon trapped in the structures below it.