Deepest Gas Sand Discoveries in North Malay Basin: Integration of Geophysical Applications and Well Data Leading to an Effective Evaluation for a Robust Development Plan, Malaysia-Thailand Joint Development Area

Adnan, M. Mohd (Carigali-PTTEPI Operating Company) | Ismail, W. Wan (Carigali-PTTEPI Operating Company) | Setiawan, A. S. (Carigali-PTTEPI Operating Company)



Integrated geophysical applications and well datasets play an important role in understanding reservoir distribution and decision making for a robust development plan. A technical assessment was completed in a gas field in the North Malay Basin to describe the reservoir heterogeneity in the Early Miocene to Late Oligocene reservoir intervals. The field is a North-South oriented plunging anticline with stratigraphic trap configuration, discovered in 2007 by Well-X1. The assessment has resulted in a proposal of an appraisal well in 2014, Well-X2ST to delineate the northern hydrocarbon extent and to assess the hydrocarbon potential in the exploration interval of deeper sequences. The new well datasets were acquired and the results were utilized to further evaluate the field.

This paper focuses on the deepest reservoir sequence, DS12, encountered by the appraisal well in the eastern flank of the Malaysia-Thailand Joint Development Area (MTJDA). Rock physics modeling and seismic attribute datasets with well log and pressure data integration were utilized to better understand sand distribution for the upcoming development planning. Due to the thinly bedded nature of the reservoirs, the seismic could not be fully utilized to evaluate internal stacking geometries. This was further complicated by attenuation from the overlying thick shale. However, attribute analysis was effective to determine overall sand presence where the bed thickness ranges from 10 to 15 meters and the seismic detection limit is approximately 8 meters.

Rock property analysis was performed to calibrate both acoustic impedance and Vp/Vs to gamma ray for indication of sand presence. The Vp/Vs derivative was used instead of acoustic impedance because of the extra information obtained in both the elastic and AVO domain. In addition, rock physics modeling was performed to differentiate gas from wet sand and shale. The seismic datasets were used to qualitatively condition a geologic model to better distribute sand presence for well planning optimization. Development wells are planned to target good quality sands to maximize recovery efficiency

The success of proving the deepest reservoir sequence in the eastern flank of MTJDA, utilizing geophysical application and well data integration, have resulted in an improved understanding to outline deep reservoir distribution in the surrounding area and mitigate uncertainties in the development plan.