摘要
利用常规组合弹簧地应力预测模型计算得到的煤层等软硬交互地层地应力数据精度较差,不能满足煤层水力压裂以及钻完井方案设计煤层气开发需要。为了进一步提高模型预测精度,分析了常规组合弹簧模型预测精度差的原因,认为主要是由于未考虑煤岩和常规砂泥岩在岩石流变特性方面的巨大差异造成的,因此引入岩石黏性系数对组合弹簧模型进行修正,得到了考虑岩石流变性的地应力预测新模型并提出了应用方法,同时结合现场数据进行了实例验证和煤层分层地应力特征正演分析。研究表明:1)相比于传统的组合弹簧模型,新模型的预测精度更高,能更有效地指导煤层钻完井和压裂设计及施工;2)在地质构造运动沉寂期,受到岩石流变性影响,煤层及隔夹层水平地应力随着时间而逐渐下降,但是下降速度不同,进而导致煤层分层水平地应力特征和层内水平地应力特征随时间发生变化,层间地应力之差甚至可能发生反转。该认识能够为当前煤层气开发中遇到的复杂分层和层内地应力现象分析提供新的视角。
The ground stress data of soft and hard interaction strata such as coal seam calculated by conventional combined spring ground stress prediction model is poor in accuracy, it can not meet the needs of coal seam hydraulic fracturing and the design of drilling and completion scheme. In order to further improve the prediction accuracy of the model, the reasons for the poor prediction accuracy of the conventional combined spring model are analyzed, and the main reason is that the huge difference in rock rheological properties between coal rock and conventional sand and mudstone is not taken into account. Therefore, the rock viscosity coefficient is introduced to modify the combined spring model, and a new in-situ stress prediction model considering rock rheological properties is obtained and the application method is proposed. At the same time, combined with the field data, the case verification and the forward analysis of strata stress characteristics of coal seam are carried out. The researches show that: 1)Compared with the traditional combined spring model, the new model has higher prediction accuracy and can guide the design and construction of coal seam drilling and completion and fracturing more effectively;2)In the quiet period of geological tectonic movement, the horizontal stress of coal seam and interlayer decreases gradually with time due to the influence of rock rheology, but the rate of decrease is different, which leads to the change of the horizontal stress characteristics of coal seam and the horizontal stress characteristics of coal seam with time, and the difference of the inter-layer stress may even reverse. This understanding can provide a new perspective for the analysis of complex stratification and bedding stress phenomena encountered in current coalbed methane development.
作者
张玉亭
ZHANG Yuting(CNOOC China Limited,Beijing 100020,China)
出处
《非常规油气》
2023年第2期115-120,共6页
Unconventional Oil & Gas
关键词
煤层分层地应力
预测模型
岩石流变性
应力松弛
规律分析
coalbed layered in-situ stress
prediction model
rock rheology
stress relaxation
feature analysis
