VSP与偏移剖面时差形成原因分析及时深调整方案

Cause analysis of the time errors between VSP and migration section and the time-depth relationship adjustment scheme

时深调整涉及VSP时深关系和偏移剖面两个方面,因此要弄清时深调整的真正原因,需要对VSP时深关系和偏移剖面及其两者存在的时差进行详细的分析.根据引起VSP时差的不同情况,将钻遇不同地质情况的井划分为水平地层、倾斜地层、断层附近及靠近高速地层四种情况,研究四种不同情况下时深标定中影响时深调整的主控因素,明确了倾斜地层、钻穿断层、靠近高速地层处都会引起VSP时差.在偏移剖面时差分析中,明确了纵向速度拾取不准是引起偏移剖面时差的主控因素.在VSP与偏移剖面时差分析的基础上,制定了不同情况下的时深调整对策,为精细时深标定和中深层储层预测提供了保障和依据.

The time-depth relationship adjustment involves VSP time-depth relationship and migration section. Therefore,in order to make out the real reasons,we need to analyze time errors between VSP time-depth relationship and migration section in detail.According to the difference situations caused VSP time errors,the drilled difference stratums are divided into four types,including horizontal strata,inclined strata,near fault strata and close to high velocity layer strata. We studied the main controlling factors of four difference situations, which effected the time-depth relationship adjustment,and figured out that VSP time errors would occurred when wells drill inclined strata, fault strata and close to high velocity layer strata. Through the reasons analysis of migration section time errors,we make out that the pickup inaccuracy of longitudinal velocity is the main controlling factor. Based on the time errors analysis, we formulate the time-depth relationship adjustment measures in difference situations,which will provide guarantee and proof for the fine time-depth calibration and middledeep depth reservoir prediction.