Liuhua 11-1 Field, South China Sea: A shallow carbonate reservoir developed using ultrahigh-resolution 3-D seismic, inversion, and attribute-based reservoir modeling

Abstract

Liuhua 11-1 Field is 130 miles southeast of Hong Kong in 1000 ft of water (Figure 1). The field, discovered in 1987, is being developed by the consortium of BP Amoco, China National Offshore Oil, and Kerr-McGee. The reservoir zone at 3850 ft subsea is producing 16–22° API oil through 25 long-radius horizontal wells. Success depends on limiting bottom-water production, which in turn makes accurate reservoir description critically important. Figure 1. Pearl River Mouth Basin index map and geologic setting. To better define reservoir heterogeneity, an ultrahigh-resolution 3-D seismic survey was acquired in July 1997. Acquisition was conducted during calm seas with short (1500 m) streamers and shallow (3.5 m) tow depths. The 180-Hz field data, enhanced during processing, produced peak frequencies of 240 Hz. Approximately four million traces were processed at a bin spacing of 5 × 5 m over 100 km2. The seismic data were first converted to acoustic impedance by using geologically constrained inversion techniques and then to porosity based on a linear impedance versus porosity relationship. Drilling data were integrated to create detailed maps of reservoir structure and stratigraphy. Petrophysical data and modeling were combined with the seismic inversion to create a spatial distribution of porosity, permeability, and saturation. Faults, fractures, and solution-collapse phenomena were analyzed using coherence technology. Complex attribute analyses added additional understanding of rock matrix continuity. This information has been used to build reservoir characterization and simulation models, that have been tuned and validated using history matching, to predict future reservoir performance. The geoscience interpretation and characterization of the reservoir for simulation are the focus of this paper. Liuhua reef carbonates are composed largely of shallow-water foram-algal packstones and boundstones belonging to the Miocene Zhujiang Formation. In-place reserves are projected at 1.2 billion barrels over the entire closure. Only the western part of …