Φ177.8mm偏梯形螺紋接頭套管脫扣原因分析
Analysis of Causes for Pull-out of Φ177.8 mm Casing with Buttress Thread Connection
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摘要: 對(duì)Φ177.8mm偏梯形螺紋接頭套管脫扣原因進(jìn)行了詳細(xì)的試驗(yàn)分析,認(rèn)為套管脫扣與套管材質(zhì)無關(guān)也不是過載所致。模擬現(xiàn)場(chǎng)脫扣時(shí)的受載情況,采用套管實(shí)物進(jìn)行驗(yàn)證試驗(yàn)。通過對(duì)套管脫扣之前的上扣配合狀態(tài)、脫扣時(shí)所受載荷和實(shí)物驗(yàn)證試驗(yàn)的綜合分析,認(rèn)為套管脫扣的原因是由于上扣不到位,在后續(xù)洗井作業(yè)過程中套管接頭受到振動(dòng)等載荷后首先發(fā)生松動(dòng),隨后在碰壓作業(yè)過程中發(fā)生脫扣。Abstract: An thorough investigation on pull-out of the Φ177.8 mm casing with buttress thread connection based on analysis via relevant tests. As a result, it is identified that the pull-out problem is caused neither by the casing material nor by the over loading condition. The load imposed on the casing connection as pull-out in operation is simulated, and verification test is conducted with real casings. Comprehensive analysis is carried out based on the above mentioned activities together with the thread stabbing state before the tripping. It is concluded that the casing tripping is due to the fact that the connection threads are not made up to normal powertight position, which leads to firstly loosing of the casing connection during the flushing operation as follows due to loads upon the casing connection like vibration, and then occurrence of the pull-out failure in the course of well pressure build-up.
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