Sichuan ~ Kawaminami Transition Zone Xujiahe Reservoir Prediction

The transition area in middle-south Sichuan Basin is part of trasition areas from paleohigh flat in middle of Sichuan Basin to high structure in southeast of Sichuan Basin, with extensive areas of Tongnan, Moxi, Anyue, Hebaochang and Jieshichang. Recently, the area has been specified as a well prospect on oil & gas abundance, due to gas gain on Xujiahe formation from Tongnan well 1#, well2# and well5# in succession. For exploration expansion, the thesis take Tongnan, Anyue areas as an important consideration, making a research on reservoir prediction on Xujiahe formation. The main achievements as followings:1. The longitudinal distribution law and reservoir logging response characteristic of sandstone and mudstone on Xujiahe formation in Tongnan area, including low gamma, high sonic interval transit time, low density, high neutron and low resistance under high resistance condition, have been recognized by lithology interpretation on the method of multi-parameter mathematics comprehensive judgement.2. Reflection horizon and reservoir seismic response characteristics, including reflected wave dropping, reflection event vibration energy reducing, event continuity turning down, the polarity of reflection event reversal and etc, have been specified by seismic reflection horizon interpretation and reservoir demarcator on method of seismic synthesis records.3. The conclusion, suitable for prediction technology on sandstone on Xujiahe formation at this area by seismic references passing wells, is that: making a sandstone prediction through gamma inversion at first; then making a combination of velocity profile by strata inversion and lithology profile with gamma<90API, with shale got rid of; finally making a transform of velocity section without shale to the porosity section, and the level with porosity >6% would be the beneficial reservoir.4.The distribution characteristic on plane and profile on Xujiahe formation has been indicated by special seismic process on 12survey lines (total 420.57km at Tongnan area) and the comprehensive prediction on reservoir distribution. On Tongnan structure, reservoir on Xujiahe 1 (section 1 on Xujiahe formation) and Xujiahe 4 (section 4 on Xujiahe formation) has existed commonly, while the reservoir thickness on Xujiahe 2 and Xujiahe 4 distributed from 10～70m and 25～75m respectively. Totally speaking, on the scope of survey lines of Tongnan structure, two generous reservoirs are existed on Xujiahe 2 and Xujiahe 4: from Fueryan to Shuangjiangzheng area and Shuanghekou to Sanhuichang, Tangba, wangjiachang area, moreover, the reservoirs are nearly overlapped.