Review of Case Histories of Two Shallow-Gas Reservoirs in China

Shallow-gas reservoirs (SGRs) in Shengli Oil Fields of China are mostly lenticular lithologic gas reservoirs controlled by structures, which are small-sized scattered gas reservoirs different from mid-deep structural reservoirs. Before 1980s, development of SGR often relied on experience to meet the need of practical gas demand, and matching techniques could not come into being. From middle term of 1980s, as gas being in short supply, a series of studies have been launching and better results have been getting. Gudao and Gudong shallow-gas reservoirs are two biggest SGRs in Shengli Oil Fields, which have similar geological factors but obviously different development results. Based on brief introduction on main geological characteristics, this paper describes chief similarities and differences and indicates some problems that should be paid attention to during gas production. Major methods used in Gudao include utilizing abandoned oil wells and/or water injection wells transferred as gas wells originally, high rate of gas production, later sand control and fine gas reservoir characterization during last production stage. Comparison with Gudao, which has better geological factors, overall development results of Gudong are advanced, such as ultimate recovery factor and utilization efficiency of gas wells etc. The main reasons including six aspects are as following: 1. Pay much attention to basic geological research. 2. Optimized gas reservoir engineering design. 3. Utilization of gas recovery techniques such as initial sand control. 4. Adoption of economic and effective measures such as drainage gas production during mid-later production stages. 5. Following the tracks of development plan and finding production potential continuously. And, 6. Introduction of modernized reservoir management methods. There are particular geological characteristics and development laws for SGR. So long as scientific and reasonable development strategies are taken, development results and economic benefits like mid-deep structural reservoirs could be gained as well.