The Computation Of Limit Fluency For Reinjection Well In Chuanzhong Oil-gas Field

With the great number of gas recovered,the production of gas field water was increasingrapidly annually.To protect the environment，much more attentionhas been paid to the waterpollution in the society.Many specialists researched the theory of water-injection whichfocused on water pretreatment， index of water quality,technological process,etc.Therecovered water injected in reservoir before series of purification.The highly density of layer and high pressure which makes reinjection mucu moredifficultly.In order to solve the problem of water injection not only will solve the aboveproblem, themain task is to find the actual situation of underground,to clear the limit capacityand to ensure the water all reinjected.Then we will lay a solid foundation to protect theenvironment.In this paper, water injection layer optimizated from13layer and14wells in the LG area,finalized the J2S as the re-injection layer. The thickness of J2S is1060~1416m, buried2600m about the depth of1200to meet the formation water reinjection requirements,development of sandstone, sandstone porosity distribution range of4.89%to7.57%with anaverage porosity of6.56%, with the ability to penetrate is2.5×10-3μm2. There is a staticpressure test for two wells which include010-U3,010-U7by Sichuan Petroleum well testteam on May12,2011, the test value is6.73Mpa.From the value we can conclude theinformation in layer is of energy deficit and potential space for re-injection.J2S in the LG area is of low permeability and tight reservoir，in which seepage law is nolonger in line with Darcy’s law. To meet the non-Darcy slow seepage law，we introducedstarting pressure gradient in the law. Through to improve capillary equilibrium method of coresand, Sec12of the starting pressure gradient experiments, the experimental values tocalculate the radius of the injection spread. The experimental methods advantages:①capillary column move more sensitively reflect the cores of fluid flow, which is easy todetermine the scope of the minimal starting pressure, and effectively shorten the measurementtime;②pressure gauge read the pressure value, greatly increasing the minimum start pressuretesting accuracy;③equilibrium process in the record column position and precisioninstrument readings to ensure the accuracy of the determination results;④apply to theminimum starting pressure of the single-phase, two-phase flow test.According to the log data, log interpretation and perforation data analysis, we confirmthe effective thickness of the real percolation capacity of the single well; using the knownphysical parameters of sandstone, fracture pressure and effective swept radius values calculated by the starting pressure gradient and a simple material balance method to computethe limit injection quantity. Correspondence between the injection rate and volume is notsimple, but to meet the actual injection dynamic. Injection pressure is different from thewellbore to the formation. Capacity of water absorption is the strongest near wellbore anddescending to the boundary.Distribution of water injection in the spread radius is ofladder-like.