碎软煤层密闭保压取心钻具的设计与室内试验

Design and preliminary experiment of sealed pressure-holding coring tool for crushed soft coal seam

摘要:

煤层气含量是表征煤储层特征的关键参数，提高煤层气含量测试结果准确度最为直接有效的途径就是采用密闭保压取心技术，把煤心样品密封在钻具内，提至地面进行解吸。本文提出了一种用于碎软煤层的绳索打捞提拉翻转球阀式密闭保压取心钻具技术方案，对该密闭保压取心钻具的工作机理及关键技术开展研究，详细阐述了该钻具的总体结构方案、主要零部件的结构设计计算、室内试验及优化改进方案。研究和试验表明：该密闭保压取心钻具结构简单、密封效果好、操作方便、可获得尽可能大的岩心直径（118 mm口径钻孔可获取直径50 mm的岩心）；带动球阀翻转的拨杆和拨环尺寸的精确配合是决定球阀能否顺利翻转、实现密封的重要因素。

Abstract:

Coalbed methane content is a critical parameter for characterizing coal reservoir properties. The most direct and effective way to improve the accuracy of the test results of coalbed methane content is to use sealed pressure-holding coring technology， wherein the coal core sample is sealed inside the drilling tool and lifted to the ground for desorption. This paper proposes a technical scheme for a wireline-retrievable lifting and tilting ball valve type sealed pressure-holding coring drilling tool used for crushed soft coal seams. The working mechanism and key technologies of the sealed pressure-holding coring drilling tool are studied， and the overall structural scheme of the sealed pressure-holding coring drilling tool， the structural design calculation of the main components， preliminary indoor experiments， and optimization improvement plans are elaborated in detail. Research and experiments have shown that the sealed pressure-holding coring drilling tool has a simple structure， good sealing effect， easy operation， and can obtain the maximum feasible core diameter （a core diameter of 50mm can be obtained from a 118mm diameter borehole）； The precise fit between the lever and the ring that drives the ball valve to flip is an important factor in determining whether the ball valve can smoothly flip and seal.