oa Fractured Basement Exploration Case Study in Malay Basin

Oil and gas exploration in Malay Basin started by ESSO and CONOCO in early 1970’s targeting on the clastic play. CONOCO focused the exploration for clastic play over southern Malay Basin Concession area. Many discoveries were made after drilling several exploration wells. In Anding, the discovery wells tested oil in clastic Group K and L reservoir sands and the wells were TD’ed in the basement. In 1978, CONOCO relinquished it acreage and the exploration effort continued by PETRONAS Carigali Sdn Bhd (PCSB) with oil and gas discoveries were made in clastic play. By 2004, with the initiative of Southern Malay Basin Exploration Team, PCSB drilled a new structure to the north of Anding field and discovered oil. The new oil discovery was the first fractured basement discovery in Malaysian Basin (Figure 1). A total of six (6) exploration/appraisal wells were drilled with the main objective is fractured basement in Anding area. Based on the well results, the optimum well trajectory was established for exploring in fractured basement play over southern Malay Basin (Figure 2). Surface outcrop study also was carried out at Redang island and surrounding areas (ca. 200km NW of Anding) to firm up the fractures trend and surface analogue for exploration drilling in fractured basement. A consistent shear fractures trends demonstrated by FMI data from Anding wells was observed on the surface outcrops. The existing of surface fractured basement at Redang Island is a good analogue for indepth studies of fracture distribution and its connectivity within basement reservoir. With the comprehensive study on the fracture distribution and connectivity within fractured basement play, optimum well trajectory to be planned in future for exploration and production management of the hydrocarbon resource in Malay Basin (Figure 3). Based on existing wells drilled into the basement in Anding area, new hydrocarbon trap model was introduced. The hydrocarbon accumulation potentially trap in clastic sandstone overlying the basement and in fractured basement as a single fluid system to be existed in Anding field. Integrated fracture study for Anding basement is recommended in order to have a comprehensive and integrated analysis of the distribution and effectiveness of fractures in Anding field prior to early monetization of hydrocarbon resources in Group L and fractured basement reservoirs.