严重出砂井中采油套管损坏的力学分析

对于出砂严重的疏松砂岩油藏,非均匀载荷也是引起套管损坏的一个重要因素。针对此类油藏中非均匀载荷的形式特点,根据弹性力学理论,建立了3种适用于严重出砂井的套管承受非均匀外载的力学模型,包括套管承受椭圆形外载力学模型、对径集中载荷力学模型以及正交对径集中载荷的力学模型,并采用逆解法进行了求解,得到了此3种非均匀载荷下套管的抗挤强度计算公式,为研究严重出砂地层中非均匀载荷作用下的套管挤毁问题提供了初步的理论依据。研究表明,套管承受3种非均匀形式载荷的能力远远低于API抗挤强度,约为均载情况下的3%~25%,其中套管在对径集中载荷作用下最易发生破坏;另外,随着套管承受椭圆形外载的非均匀程度逐渐降低,其抗挤强度逐渐升高。

MECHANICAL ANALYSIS OF PRODUCTION CASING DAMAGE IN SEVERELY SANDING PRODUCTION WELLS

Non-uniform loading is one of the important causes leading to casing damage in unconsolidated sandstone reservoir with severely sanding production.Considering the characteristics of non-uniform loading,this paper has established three mechanical models of casing fit for the wells with severely sanding production under non-uniform loading(such as elliptical loading,diametral concentrated loading and orthogonal diametral concentrated loading),and based on the elastic theory,the formula that can calculate casing collapsing strength under the non-uniform loading has been obtained,which can help to study casing collapsing in unconsolidated sandstone reservoir.Research shows that the casing collapsing strength under non-uniform loading is far less than that given by API,and is about 3%~25% of that under uniform loading.Among the three mechanical models,casing can be collapsed most easily under diametral concentrated loading.Also,casing collapsing strength increases with the decrease of nonuniform degree of elliptical loading.