Abstract
Five wells of L oilfield in Bohai bay basin have drilled 10 - 15 meters thick oil layer in the Paleogene delta. Due to the deep-buried reservoir and the poor seismic performance, it is difficult to identify the reservoir genesis, and predict reservoir distribution. By analyzing core, well logging and seismic data, a stable mudstone section is selected as the correlation marker to establish a stratigraphic framework. The paleogeomorphology is reconstructed after decompaction correction and paleobathymetric analysis. Based on the differences of paleotopography and sedimentary facies, the study area mainly develops two delta systems: low gradient coarse-grain delta system and steep gradient delta-turbidite system. The favorable reservoir of low gradient coarse-grain delta, which is thick and has good lateral connectivity, mainly locates in the delta front. The favorable reservoir of steep gradient delta-turbidite system locates in the delta front and turbidite facies, and the delta front deposits are thin and have poor lateral connectivity. The boundary of delta front is first depicted on the basis of paleotopography. In combination with reservoir architecture and forward modeling analysis, the seismic attribute is then optimized to predict the distribution of favorable reservoir. Using this method, several sets of oil-bearing sandbodies have been drilled in L oilfield, and the prediction accuracy of reservoir distribution is proved to be high. This study demonstrates that the paleogeomorphology plays an important role in controlling the genesis and distribution of the delta reservoir and provides reference for the reservoir prediction in similar oilfields.
Highlights
The L oilfield is a delta reservoir with proven recoverable oil reserve of nearly 100 million tons
This study demonstrates that the paleogeomorphology plays an important role in controlling the genesis and distribution of the delta reservoir and provides reference for the reservoir prediction in similar oilfields
This study proves that the slope plays an important role in controlling the formation and distribution of delta reservoirs and provides reference for reservoir prediction of similar oilfields
Summary
The L oilfield is a delta reservoir with proven recoverable oil reserve of nearly 100 million tons. Five wells have drilled thick reservoir (10 - 15 meters) under the group I, with newly discovered reserve of nearly 10 million tons, and it is one of the targets with great potential. The study of delta characteristics and slope is of great significance for predicting reservoir distribution. Wang et al (2003) studied the control of slope on sedimentary distribution in the depression lake basin. The paleogeomorphology is restored to study its control on distribution of reservoir. This study proves that the slope plays an important role in controlling the formation and distribution of delta reservoirs and provides reference for reservoir prediction of similar oilfields
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