煤层地面井保压取心控制器闭合轨迹模型

Closure trajectory model of pressure-preserved controller for coring in coal seam surface well

传统煤层勘探方式采用开放式取心工具获取煤样,并通过理论估算的方式计算损失气。导致所测得的煤样含气量普遍偏低,严重制约煤层气开发利用,影响煤矿安全开采。为满足深部煤层勘探需要,创新设计了一款煤层地面井保压取心工具,工具总长6.7 m,单次可取保压煤心样品3 m。为提高深部煤层保压取心可靠性和成功率,构建了孔底液体环境下保压控制器闭合轨迹模型,并通过实验测试和理论推导获取了控制器触发弹片弹力转矩的变化曲线。为验证闭合轨迹模型的准确性,了解保压控制阀盖在钻井液环境下的翻转闭合过程,进行了保压控制器触发闭合室内实验。结果显示,实验所测得阀盖运行轨迹与理论计算结果的偏差小于5%,验证了模型的准确性。在此基础上,优化了煤层地面井保压取心工具内保压控制器触发系统,并在深度为30 m的试验井下,密度1.1 g/cm^(3)、黏度60 s的膨润土基泥浆环境中进行了8次孔底抽拉触发实验,保压控制器均能稳定闭合,成功率为100%,并能保证压力在14 MPa时连续工作至少350 min无泄漏,证实了保压控制器触发系统的可靠性。本文所建立模型可以实现井下保压控制器运行轨迹预测,进而可以针对不同钻井液体系设计、优化触发系统,从而提高深部煤层保压取心成功率。

The traditional method of coal exploration is to obtain coal samples using an open coring tool and estimate the gas loss through theoretical calculations.However,the measured gas content of these coal samples is generally low,significantly impeding the development and utilization of coalbed methane and compromising the safety of coal mining operations.To meet the demands of deep coal exploration,an innovative pressure-preserved coring tool was specifically designed for the coal seam surface wells.This tool has a total length of 6.7 m and can extract a 3 m long pressure-preserved coal core sample at a single time.In order to enhance the reliability and success rate of pressure-preserved coring in deep coal seam,a closure trajectory model was constructed for the pressure-preserving controller operating in a downhole fluid environment.Meanwhile,the variation curve of the elastic torque for the triggered shrapnel of the pressurepreserved controller was obtained through experiments and theoretical derivation.To validate the accuracy of the clos ure trajectory model and gain insights into the flipping and closing process of the pressure-preserved control valve cover in a drilling fluid environment,laboratory experiments were conducted to trigger the closure of the pressure-preserved controller.The results indicate that the measured moving trajectory of valve bonnet in the experiments has a deviation less than 5%from the theoretical calculations,verifying the accuracy of the model.On this basis,the trigger system of pressure-preserving controller within the pressure-preserved coring tool was optimized.Besides,eight bottom-pull triggering experiments were conducted in a test well with a deep of 30 m in the bentonite-based mud environment at a density of 1.1 g/cm^(3)and viscosity of 60 s.In all the experiments,the pressure-preserved controller can be closed stably with a 100%success rate,and ensure no leakage for at least 350-min continuous operation at 14 MPa,thereby verifying the reliability of the trigger system of pressure-preserved controller.The model presented in this paper can accurately predict the closure trajectory of the pressure-preserved controller in the downhole,enabling the design of customized triggering systems for different drilling mud systems to enhance the success rate of pressure-preserved coring in deep coal seam.