Shallow gas reservoirs are widely distributed in China and mostly occur at depths shallower than 1500 metres (4921.50 ft). These occur as lenticular and marginal reservoirs, with small and scattered reserves, with quite complex gas-water relationship and edge/bottom water in the majority of sand-bodies. Each sand-body forms an unattached and closed gas-water system, but there is limited elastic energy in the aquifer. The production performance of one of such reservoirs is as follows:Per-well initial gas rate is rather low with fast decline.The reservoir has a gas drive to weak elastic water-drive.Water incursion has obvious influences on production results.Wellhead pressurse could be used to represent the changes of formation energy, for it is impacted little by wellbore accumulated liquid.Finally, formation damage resulting from drilling, perforating etc. has noticble influences on the gas wells' performance. Thus the main factors that could decide reasonable well rates should be the following factors: Efficient utilization of formation energy, reservoir structure should not be destroyed, accumulated liquids in the wellbore should be continuously removed. In addition better development results can be achieved through initial sand control and edge/bottom water fingering/coning should be minimised. The purpose of this paper is to have a review of the parameters and the performance of the Shengli oil reservoirs. It could be used for reference for similar type of reservoirs. Introduction According to China National Standard, Natural Gas Specification (GBn 270–88),1 shallow gas reservoirs (SGR) are buried in depths less than 1,500 meters (4921.50 ft). The source of gas includes biogas, coalformed gas, oil-type gas and water-soluble gas etc. Shallow gas reservoirs are mainly distributed in Neogene & Quaternary systems in terms of horizons and are distributed widely in China with some considerable reserves in places, such as DF1–1 gas field in Yinggehai Basin (Pliocene series),2 Hangzhou Bay (Quaternary) in southeast coastland,3 Luliang Basin in Yunnan Province,4 Bohai Bay Basin in Eastern China, Songliao Basin in Northeastern China, Sichuan Basin,5 Chaidamu Basin6 and Jianghan Basin in Hubei Province etc. According to preliminary evaluation, total reserves are up to about 2–5×1012m3 (70.6–176.6 Tcf), excluding that of water-soluble gas. But only 0.3×1012m3 (10.6 Tcf) or so of original gas in place (OGIP) has been proven. Hence there is still a wide exploration scope.

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractShallow-gas reservoirs (SGRs)

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAimed at the characteristic that gas-bearing formation of shallow gas reservoir (SGR) shows bright spot on seismic cross-section, integrative technology research combining exploration and development has been developing in Shengli Oil Fields. After several years' practice, a series of techniques of progressive exploration and development with high benefit for SGR have been created. Studies and practice prove that bright spot on conventional seismic section has nature of multi-solution, i.e. some kinds of reservoirs, such as lithologic reservoir, hydrogenous sandstone, gas bearing hydrogenous sandstone and gas bearing sandstone, all show the characteristic of bright spot. In order to solve this problem, special purpose processing involving 3D, G-log and amplitude versus offset (AVO) is used to distinguish between real bright spots and false ones. Four gas-bearing regions including Yanjia, Chenjiazhuang, Gunan and Sanhecun have been discovered and put into production since 1988. 162 probable bright spots have been found, and 60 new wells drilled with 56 successful wells. Drilling success ratio advances from 55% to 93.3%. Incremental proven gas bearing area is 48.2 km 2 with gas initially in place 4.304×10 9 m 3 , and gas rate is 375× 10 3 m 3 /d. The spread application for this technology has been seeing considerable economic benefit, and it provides practical experience for exploiting such kind of reservoirs also.Progressive exploration and development utilizing technology of seismic bright spot accelerates the step of getting production. Four steps, including special purpose processing and seismic data interpretation, programming development plan and fulfilling drilling and gas lines construction, gaining gas productivity and submitting proven reserves, are all accomplished in the same year. This paper introduces a typical example for the course of progressive exploration and development in Chenjiazhuang Arch.

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractShallow-gas reservoirs (SGRs)