Print this pageIntegrated Geological Modeling of China Offshore Reef Reservoir: A Case Study from L Oilfield, South China Sea
The offshore reef oilfields in China are mostly distributed in the Pearl River Mouth basin, South China Sea. Compared with the onshore carbonate oilfields in China, the offshore reef reservoir has their own features. The stratum is relatively younger, Neocene. Primary pores are preserved in Neocene reef reservoir. Frequent exposures into atmosphere make freshwater diagenesis and dolomitization possible. Primary pores, corrosion pores and dolomites formed very good reservoir. Besides kinds of pores, there are different kinds of fractures. Because of these characters, Neocene reef reservoir has both good property and great heterogeneity. This paper takes L Oilfield in South China Sea as an example to illuminate the reservoir characterization and geological modeling of Neocene reef reservoir.
L Oilfield is located offshore Pearl River Mouth basin. The reservoir is a typical fringing reef on the carbonate platform margin, with over 14 km2 oil-bearing area and two wells (L-1,L-2). The problem is that seismic and well log has poor relationship, which makes the direct use of seismic in modeling unfeasible. But by the incorporated analysis of 3-D seismic, cores and logs, it is possible to access the reservoir quality distribution and to build up 3-D model reasonably.
The lithofacies in the reservoir of L Oilfield include coral boundstone, algae boundstone, red algae floatstone, bioclastic rudstone. With the integration of 3-D seismic data and cores, the inner stratum frame of the reef reservoir and the possible distribution of facies inside the frame are work out. Vertically, the reservoir can be divided into 5 subzones. Horizontally, the reef can be divided into reef front, reef crest and reef flat. In the two upper zones,L-1 well and L-2 well have different lithofacies. L-1 well is located in reef crest, characterized by algae boundstone and red algae floatstone. L-2 well is located in reef flat, characterized by bioclastic rudstone.
With seismic and well date, the microfacies maps are figured out for very zone. Thus, the geological knowledge base is built up, including the reservoir property for each microfacies, its possible size, shapes and distribution. Under the geological constraint and with object-based method, 3-modeling is built up to simulate the distribution of microfacies. With experiment design method, the uncertainty of reserves is appraised and a set of models is seek out for numerical reservoir simulation.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009