The Study Of The Optimization And Decision-Making For The Artificial Interlayer In Bottom-Water Reservior

Natural bottom water reservoirs are widespread in both domestic and foreign oilfield.And some edge water reservoirs also show the similar characteristics of the bottom water reservoirs because of the fast water invading from reservoirs bottom to the wellbore due to the reservoir rhythm or the influence of gravity.The vertical well and horizontal well are the main development well type for the bottom water reservoir in our country.And the Production performance and reservoir pressure change are different between the vertical well and horizontal well.The bottom water coning is shown for vertical well due to the point contact between the vertical well and reservoirs,and the bottom water cresting is shown for horizontal well due to the line contact between the horizontal well and reservoir.The reservoir is direct contact with bottom water in bottom water reservoir,so the bottom water reservoir always has sufficient natural energy.However,the pressure drop mainly appears near the wellbore during the production process of the oil well.Thus,the oil well always has a short water free production,a fast water breakthrough and a quick water cut increasing,causing a low recovery and a high development risk.The key to study the water coning is to obtain the vertical pressure gradient distribution,which directly affects the speed of water invading and the spatial distribution of the water cone.Based on the Tarim Oilfield project,the paper derived the expression of the reservoir pressure distribution in Laplace space.And the solution in real space is obtained by numerical inversion.The reservoir pressure distribution and the characteristic parameter of water cone are obtained by the solution.Then the parameter sensitivity is analyzed.As for the vertical well producing in the reservoir with interlayer,the paper proposed an approximate model to simulate the pressure distribution near the edge of the interlayer.The mechanism of clearing water cone by interlayer and the process of back flow is explained by calculating the characteristic parameter of water cone.Based on the numerical simulation and the model proposed in the paper,the paper gives a method to choose wells and layers to build artificial barrier for vertical well producing in reservoir without interlayer.