| Low permeability reservoirs featuring with widely distriuting and large deposit is the next key object for oil exploring. Information about oil testing in Low permeabili ty reservoirs offers foundations for the exploration and development of oil reservoris. The traditional darcy seepage theory now is still being applied to the well test interpr etation model of oil reservoirs, but it is not applicable to the percolation mechanism o f extremely low permeability reservoirs due to its lack of variety in model and interpr etation method. As for such extremely low permeability reservoirs of complex percolat ion mechanism, the current research mainly focuses on the influence of a single factor on the well test interpretation model. However, when considering the factors affecting stress response, if we only take the start-up pressure gradient or the voltage-sensitive effect intoAccount without any consideration of the combined effect of other factors, we are not ableto make an effective interpretation of the reservoir parameters and to provi de timely information about reservoirs, which will inevitably have an negative impact on the economic benefits of the development of oil-gas fields and on the follow-up w ork as well. At present, there are several problems existing in the extremely low perm eability reservoirs of complex percolation mechanism, such as high probability of failu re, the rarity of radial flow stage in real test wells, variable well test interpretations. By combining the results of well test analysis with the practical conditions of oil field, the paper makes a statistical classification of the curve of real test well on site with focus on the reason analysis of abnormal curve, verifying the interpretation results of well test model of low-speed, non-darcy seepage, optimizing the model choices of w ell test interpretation. At the same time, based on the25-7-2well in Huizhou, the pa per details the role the interpretation of low permeability well test plays in predicting the productivity of oilfields and compares the oil productivity among low permeability reservoirs of different well completionsThis paper:(1) referred to more than100literatures related to well test at home and abroad. then screened out some methods in those literatures and made a analysis of them;(2) made a statistical classification of the curve of test well on site with focus on the reason analysis of abnormal curve;(3) made experiments on the start-up pressure gradient and two-phase flow of5pieces of core contained in the25-7-2well and the experimental results were analyzed;(4) conducted a research into the correlation between formation pressure and oil saturation as well as the properties of formation fluid respectively;(5) made a detailed well testing interpretation about the pressure data of the25-7-2well and then the corresponding reservoir dynamic parameters were obtained by applying seepage well test models of low permeability reservoirs which considers the start-up pressure gradient:(6) studied calculation methods concerning the productivity of open hole completion.casing perforation completion and post pressure, which is suitable for the25-7-2well.then calculated the well’s production capacity by different well completion methods and made comparisons among them.which provides a basis for choosing a well completion method in the block of Wenchang formation;(7) calculated the daily output of open hole completion, casing perforated completion, horizontal well completion and post pressure productivity when all the oil-bearings are open in the Wenchang group of the25-7-2well;(8) studied the effect of the partial degassing(the flowing pressure on the bottom hole is lower than saturation pressure) near wellbore on productivity under different completion methods of the25-7-2well to determine the best differential pressure of production. |
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