Seismic Interpretation and Depositional Model of Kais-Lower Klasafet Reservoirs inWalio Area of Kepala Burung PSC, Salawati Basin, West Papua, Indonesia

Abstract

Kepala Burung PSC is located at onshore portion of Salawati Basin. The PSC area is divided into two area(s) namely Walio Area and Arar Area at the south and north, respectively. Numerous exploratory wells had been drilled at Walio Area which resulted several economical discoveries of oil reservoired within the reefal Kais Formation and the overlying mixed-silisiclastics carbonate of Lower Klasafet reservoirs namely U-Marker and Texturalia Intervals. The latest discoveries at this area was in 2010 by the drilling of North Walio-1 well which encountered oil reservoirs within Kais Formation. With consideration of exploration success ratio, proven petroleum system elements and thebroad distribution of Miocene Kais and Lower Klasafet; exploration in this area is still promising. Moreover, twothree-dimensional (3D) volume of seismic which acquired in 2004 and 2007 are beneficial in improving the geological understanding in this area. This study is providing seismic interpretation which weighted to seismic facies analysis within Kais-Lower Klasafet reservoirs and the depositional model of these two associated reservoirs. Seismic facies analysis within the studied reservoirs are focused to reflection characteristics such as; seismic reflection termination, continuity, amplitude, frequency and internal reflection configuration. The internal seismic reflection characteristics are compared between the successful and unsuccessful exploration drilling. Subsequently, a sketched depositional model at the times of Kais and Lower Klasafet deposition is constructed. Three seismic reservoir facies are recognised in this area; pinnacle reef-patch reef which associated to narrow topography high(s), reefal carbonate bank which associated to broad or extensive topography highs, and drowning package of carbonate-mixed-silisiclastics at the top of Kais reef(s). These types of carbonates are interpreted to be deposited within five stages of major sea level rise. The antecedent topography of the reefs is mapped to be used as reef fairways in Salawati Basin, which means will be tied to neighbouring northern Arar Area and the other adjacent areas.