Prediction Of Formation Pressure And Analyses On Pressure System In Adjustment Wells

There were a lot of contrariness such as interlamination contrariness, inner interference of layer and plane contrariness in anisotropic oilfields developed by injecting water for a long while like daqing oilfield.Due to substantive polymer and water injection, pressure gradient was large between layers and partial pressure could not release in the reservoir,which rezulted that abnormal pressure area came into existence. Drilling accidents happened frequently when drilling for adjustment well such as polymer flooding well,ASP well and thrice infilling well was conducted in such condition. On this account, it was vital to exactly predict reservoir pressure in the process of drilling for adjustment well in oilfield developed by injecting water.Using reservoir description data of exploration and development, geophysics and geochemistry,and reservoir type of test area in Sana oilfield in north of Daqing placanticline, geologic feature of the area was made certain to exactly predict reservoir pressure on drilling for adjustment well.Based on theory of dynamic of fluids through porous media, reservoir performance analysis and well test analysis, theoretical model of pressure distribution was setup in different situations to predict pressure of various layers.According to calculated pressure and actual pressure,the model was used to draw picture of pressure distribution, pressure isoline and pressure traverse. Through systematical analyses of distribution feature and influencing factor of reservior pressure, wellhead pressure was exactly predicted,on the basis of which quantitative control method of abnormal pressure in adjustment well and adjustment method of pressure isoline were proposed.Field application rezults showed that the calculated pressure conformed to actual pressure with the theoretical model of pressure distribution in use. According to different pressure distribution feature in test area and aimd at reducing pressure drop in interlamination and annular space, proper control method of abnormal pressure should be chosen to adjust integrative pressure isoline.