Publications

The “B field is a three-way dip closure with a North-South trending orientation. A lower structural area or saddle, together with a small NWSE trending fault delineate “B into a northern and southern area. The “B field was discovered by the BS-1X well in 2006 and was appraised with the BS-1XST1 at the same year. The main reservoirs are in the Early Miocene Sands at depth of around 3500m tvdss. So far four wells have penetrated the structure, BS-1X & BS-1X ST1 in the south and BN-2X & KL-1X in the north. The main reservoir in “B field is Middle Dua Sand 5 (MDS5) that was deposited in a sub-littoral tidally influenced environment. For reservoir description purposes the MDS5 reservoir has been subdivided into two, 5A with predominantly poor reservoir heterolithic facies sitting above 5B blocky Gamma-Ray higher reservoir quality sand type. The seismic amplitude response over the Top MDS5 reservoir is quite complex. It is a combination between the effect of porosity, fluids and relative sand thickness (5A and 5B sands). The total thickness of combined 5A and 5B sands is approximately the same with the entire field as shown by the drilled wells. The synthetic seismic generated at each well suggests that the MDS5 seismically, represents a relatively soft sand type compared with the overlying shale. In general, the amplitude response in the northern part of the field is dimmed and is significantly brighter in southern area. As confirmed by the wells, the dimmed amplitude type in the northern area has better porosity when compared to the bright amplitude type in the southern area. A forward modeling study was carried out with objective to help understand the key contributors to amplitude response prior to further advanced processing such as Simultaneous Inversion work. The forward modeling indicates that the variation in seismic amplitude between north and south of “B area is most likely caused by 5A and 5B thickness variation rather than porosity or fluid variation. The amplitude dimming over the northern “B area is considered to have related to thicker 5A sand and thinner 5B sands. On the other hand, the amplitude brightening in the southern area is most likely caused by the well developed 5B and thin 5A sands. Based on this seismic partial stack seismic forward modeling analysis and amplitude map over MDS5, we could draw the conclusion that the northern “B field area shows more reservoir heterogeneity compared to southern area. The results also suggest that in the northern structure the heterolithic 5A sand type is more developed where in the southern part, the higher reservoir quality 5B sands type dominates.