ICE 2022


BZ19-6 condensate gas field is a big discovery in offshore Bohai Bay Basin, and more than one hundred billion cubic meters of condensate gas has been discovered in its Archaeozoic metamorphic reservoirs. However, reservoir characterization is a big challenge due to harsh operation environment and strong formation heterogeneity. To better reveal the reservoir quality and learn of the production controlling factors, advanced logging while drilling (LWD) technologies were integrated to solve the problem. First, open fractures, filled fractures and drilling induced fractures were differentiated based on LWD high resolution electrical image data and sonic data, and fracture occurrence and the maximum horizontal in-situ stress direction were obtained. Second, quantitative parameters of fractures and vugs were calculated using advanced techniques. Moreover, main production controlling factors were concluded by integrating qualitative and quantitative parameters as well as production data. Innovatively, an integrated indicator – RQI (Reservoir Quality Index) was created by combining fracture parameters, vug parameters, sonic parameters and effective reservoir thickness and it was successfully used to reveal reservoir quality and forecast well production. Based on the results of single wells, an integrated study in terms of lithology, structure position, fractures, vugs, reservoir types and effective reservoir thickness were performed for multi-wells. It is found that well production is not controlled by structure position. Wells located in lower position may have very high production, while wells located in higher position may have very low production; Well production is mainly controlled by open fractures, open vugs, reservoir types, and effective reservoir thickness. High production wells normally have 3 characteristics: (1) small angle difference between the strike of natural fractures and the maximum horizontal in-situ stress direction, usually less than 30 deg; (2) more fracture-pore reservoir types and better connectivity; (3) high reservoir quality index (RQI), usually more than 20. LWD tools managed to provide high quality logging data even with static temperature up to 195 degC for highly deviated wells. And the achievements of the integrated study have dramatically improved the geological understanding of the reservoir and provided valuable information for deployment of new wells and production forecast.