インドネシア，東カリマンタン，Ｋｕｔｅｉ堆積盆地北部，マハカムデルタ沖合，サデワガス田の中部〜上部中新統スロープチャネル砂岩貯留岩―試探掘井および三次元地震探鉱データに基づくチャネル砂岩体モデリング―

Abstract

Sadewa Gas Field, a deep-water field discovered in 2002 in East Kalimantan, is located on the current continental slope at water depths ranging from 1,000 to 2,800 ft, offshore Mahakam delta, north Kutei Basin. The Mahakam delta, initially developed in the Early Miocene, contains several giant oil and gas fields. Reservoirs of such fields were deposited in shallow-water, deltaic environments on the shelf. Sadewa, on the other hand, was located on the slope that linked shelf-edge deltas to the deep-water sediments on the basin floor during the Middle and Late Miocene. It is interpreted that small-scale deltas developed along the shelf edge during lowstands (lowstand deltas), fed slope channels and then the basin floor with the coarse sediments. Cores of the Sadewa reservoir rocks exhibit episodic turbiditic deposition of reworked delta sediments.Slope channel sandstone reservoirs of Sadewa field were detected as high-amplitude anomalies in 3D seismic data. Channel-like features on seismic amplitude maps were selected as exploratory drilling targets. The subsequent drilling of 8 exploratory wells resulted in encountering sandstone reservoirs as predicted.The following procedures were carried out to model channel sand-bodies. First, the three-dimensional distribution of the sand-body of each channel (reservoir framework) was created in Petrel software based on the combination of seismic and well data. Second, this channel framework was filled with two facies, i.e. channel and levee/overbank facies, and with the petrophysical parameters unique to each horizon and facies. Lastly, gas-liquid contacts of proved, probable and possible ranges were input based on the well results. The reservoir model thus created was subjected to the reservoir simulation to estimate recoverable gas volumes.Although located in the deep water, by taking advantage of the vicinity to the shelf, Sadewa field will be developed by extended reach wells from the shelf edge in 285ft of water.