Study On The Skin Coefficient Of Screen Tube Effecting Of Collapse Of Sand And Mud Interlayer In Horizontal Wells

In order to prevent the collapsed blocks from blocking the wellbore,a combination of blind tubing and screen tubing is usually used to protect the wellbore and improve the recovery rate.However,in engineering practice,it was found that the sand and mudstone particles collapsed in the blind tubing section may accumulate and move to the screen tubing section to block the screen tubing under the action of fluid,contaminating the annular skin and causing a decrease in production capacity.The first is the accumulation-transportation-clogging law of collapsed sand particles in the annulus of the screen tube,and it is necessary to clarify whether the annulus is clogged or not,and how different blind-tube to screen-tube ratios at different flow rates affect the degree of clogging of the annulus of the screen tube,but there is a lack of theoretical research methods for this study.Secondly,if plugging occurs in the annulus,the influence of different mud content and different blind-to-screen pipe ratios on the annular skin coefficient should be clarified,but there is no research device for the blind-to-screen pipe combination completion method to test the annular skin coefficient.Third,in field wells,the degree of impact of sand mudstone collapse on capacity is not clear,and capacity assessment is needed.Therefore,this paper addresses the above problems,mainly through the methods of numerical simulation and indoor tests,and combined with field data,to provide a theoretical basis and reference for oilfield field engineering practice.The main research content of this paper is divided into the following three aspects:(1)First,a set of numerical simulation methods for particle transport in the combined blind pipe-screen pipe completion method is established,and the accumulation-transport-blockage law of mud and sand particles in the annulus at different flow rates is studied by CFD-DEM numerical simulation.It was found that:(1)at flow rates lower than 0.5m/s,the size of the blind sieve ratio has little effect on particle transport and blockage,and particles accumulate in the blind section,and particles hardly move and the sieve tube does not block.(2)Flow rate is greater than0.5m/s,the blockage of the screen tube increases with the increase of the screen tube length ratio,and the particles accumulate in the annulus of the screen tube section.(2)Second,a set of fully visible blind pipe-screen pipe combination epidermal coefficient testing experimental device was developed independently,and the epidermal coefficient testing experiment was conducted through indoor physical simulation experiments.(1)The effect of the mud content and the ratio of blind pipe to screen pipe on the epidermal coefficient of the sand accumulated in the annulus of the screen pipe was investigated,and the flow rate and pressure drop data were obtained through the experiment.(2)In the case that the annulus is not completely filled,the epidermal coefficient is less than 0.2,and the effect of blind sieve proportion and clay content on the epidermal coefficient is negligible.When the annular void filling rate is 100%,the larger the blind sieve ratio and clay content,the larger the epidermal coefficient.(3)Third,the degree of impact of sand mudstone collapse on capacity was investigated by conducting a capacity assessment of the field wells.The capacity evaluation model of horizontal well bare-hole completion and sieve pipe(perforated pipe)was used,and the capacity evaluation index of equivalent capacity ratio was introduced to evaluate the capacity of horizontal wells XX34-1-A6 H and XX23-1-4H.The length of sieve pipe(perforated pipe)into the mudstone section was studied,and the optimal selection of tubing column under the blind pipe-sieve pipe combination completion method was suggested,which provides guidance for field engineering practice and effectively reduces the completion risk caused by collapse of sand mudstone interburden.