The Computation Of Limit Fluence For A Single High-pressure Reinjection Well & Study Of Injection Increase Mechanism In Chuanzhong Oil-gas Field

With the demand of natural gas increasing, the production has been increasing annually.So more gas field water has been recovered. For reducing the cost and protecting the environment, usually the gas field water has been reinjected into reservoirs. At present,gas field water is re-injected by high-pressure methods in Chuanzhong oil-gas field.This method not only resolvs problems related to environmental protection but also prevent water pollution, but also save money for the oil and gas fields. But with the rising water cut a large number of old wells and new production wells into production, water production increased rapidly, so the main problem that is a large number of produced water re-injection is to be solved.In this paper, in order to satisfy the needs of the development of water reservoir for water re-injection wells,based on water re-injection wells for gas dynamic monitoring and analysis and evaluate of re-injection wells, these are in Chuanzhong oil-gas field ,at below the rupture pressure of injection capacity and pressure trends. Based on the Darcy formula, we research on the actual situation of water injection wells about Chuanzhong oil-gas field,so we derived stable and unsteady seepage flow model based on Chuanzhong water Injection,while we clearly recognized re-injection well pressure, re-injection amount and distribution so that we find out relationship between the relevant parameters about water injection wells in the injection process, and analyzes the main factors affecting reservoir absorbent.In this paper, we research on re-injection effects, and injection water quality impact on the mechanism of reservoir flow properties and recharge layer into the ability of research, based on existing circumstances of water injection wells about Chuanzhong oil-gas field. The main achievements of this paper are as follows: (1) Water absorption Indices can reflect the absorption capacity of the size of the injection layer. there is a certain correlation between the index of water absorption and accumulation time of water injection. With the injection time continuously increasing, these is the downtrend in curves of the index of water absorption. but when the measures of augmented injection taken by injection occurs ,it is take place jump on curves of the index of water absorption.(2) Based on analysising water absorption index and using Hearn experience and combined with stable seepage flow model and the material balance equation flow model about work area,the formula of the reciprocal of apparent injectivity index and cumulative water injection was derived. The curve between reciprocal of apparent injectivity index and cumulative water injection is a linear relationship in the semi-logarithmic coordinates.(3) Base on injection model about Hall, the Hall characteristic curve of injection wells was drawn. Through studying the cumulative water injection and injection pressure accumulation we know there is approximately linear relationship which is generally more than 97% in Cartesian coordinates. Through the Hall characteristic curves the relationship between slope of the curve and the permeability of reservoir was derived. The reservoir permeability was calculated by the actual reinjection data.(4) It studies that application of Hearn and Hall curves flow well test can replace the stair-like flowrate well test, so turn up the pressure in the injection wells but below the formation fracture pressure of injection, the highest amount of water to speed up compensation for oil deficit, and promote effective water injection. Application Hearn and Hall curve method can also detect changes of reservoir conditions.According to pump pressure must be no more than the design limit pressure, and do not affect normal production conditions around the gas well,so that we definit the limit fluence of reinjection wells. Considering the formation rock and fluid compressibility derived formation to accommodate the volume of injected water law model. based on determining the model various parameters, we calculate the limit fluence of reinjection wells in the design of the injection pump pressure by using the model.With the Hall thought and considering the cumulative effect of pollution,we derive four-dimensional linear water injection model in the law of water injection. It verifies that the model can well describe injection wells law of the water injection performance in Chuanzhong oil-gas field (correlation coefficient is above 0.97). And useing the model we predict pressure injection pump up the law, calculate the maximum pressure injection pump maximum formation time and the maximum amount of water injection. The model can describe a single well into the ability of factors.It can provides a theoretical basis in scientific and efficient water injection for Chuanzhong oil-gas field.