地层承压能力固井前动态测试方法

Dynamic testing of formation pressure bearing capacity before cementation

固井前获得地层的实际承压能力,对固井设计和安全都有着重要的意义。在一些上层套管下深较浅的井中,受上层套管鞋处地层破裂压力或上层套管抗内压强度限制,常规的地层承压能力测试无法满足固井要求,针对该问题,文中提出一种地层承压能力动态测试方法,同时进行了现场应用。该方法是在下套管循环后分挡逐渐增加排量,并同时记录与之对应的泵压、钻井液性能及漏失情况,然后利用流变学的原理计算出关键地层深度的承压能力。研究认为这种动态承压测试方法对于低压易漏井行之有效,实用性强,能够满足固井现场对承压能力测试的要求,获得的地层承压能力值为固井设计和安全提供了基础和保障。

It is very important to the cementation design and safety to obtain the actual pressure bearing capacity of formation before cementing.The conventional formation integrity test(FIT)can not meet the cementing requirements due to limits of the formation fracture pressure at the upper casing shoe or the upper casing resistance to internal pressure.An innovative dynamic testing method was proposed in this paper to eliminate this issue and used in the field.This method operates as:increase flowrates at different levels after casing RIH and circulation,record the corresponding pump pressures,drilling fluid properties and amounts of leakage;then use rheology to calculate the formation bearing capacity at critical depths.Study indicates that the dynamic pressure testing method is effective for low pressure leaking wells,and very practical,meeting the FIT requirements for well cementation.The formation pressure testing results provide the basis and guarantee for the cementing design and safety.