砂岩油藏地应力及岩石力学参数与套管损坏相关性

THE CORRELATIONS BETWEEN GEOLOGICAL STRESS AND CASING DAMAGE AND BETWEEN ROCK MECHANICS PARAMETERS AND CASING DAMAGE IN SANDSTONE RESERVOIR

XMAC测井仪能够在井下进行连续测量,不仅能测得储层各沉积单元的最大和最小水平主应力以及最大水平主应力方位,而且可以取得密度、破裂压力、泊松比、杨氏模量、剪切模量等岩性及力学参数,从而有助于研究储层纵横向岩石力学特征,进而为确立地应力与套管损坏之间以及岩石力学参数与套管损坏之间的相关性提供技术支持。研究结果显示,与非套损区对比,标准层成片套损区的主应力及破裂压力很高,泊松比很大,剪切模量很小,这种力学特征可用来确立标准层成片套损区的形成或存在;与正常井区相比,油层部位套损集中区的主应力及破裂压力偏高,泊松比比较大,剪切模量比较小,主应力方位发生偏转,可利用这种力学特征判断油层部位套损集中区的形成或存在;破裂压力变高、泊松比变大、剪切模量变小、差异应力较大是导致标准层部位发生套损的内在原因,而区域之间的平面应力差异是导致标准层部位发生套损的外在推动力;泊松比大、剪切模量小、破裂压力高等岩石本身力学特征是油层部位发生套损的内因,而地应力场和地层压力场的改变是油层部位发生套损的外因,油层部位套管损坏是内因、外因共同作用的结果。

XMAC logging tool is able to continuously measure in underground. For every reservoir sedimentary unit, it can not only measure the maximum horizontal principal stress, minimum horizontal principal stress, the maximum horizontal principal stress orientation, but the lithology mechanical parameters can be obtained, such as density, fracture pressure, poisson＇ s ratio, young＇ s modulus, and shear modulus. It will help us to study rock mechanical characteristics of the reservoir. So the technical supports will be provided for us to determine the correlation between geological stress and casing damage, and to establish the correlation between rock mechanical parameters and casing damage. Compared with non-casing-damage area, the principal stress and fracture pressure was very high, poisson＇ s ratio was large, and the shear modulus was small in the larger index bed casing-damage area. So the mechanical characteristics can be used to establish the formation or existence of casing damage area in the standard layer. Compared with the normal well area, the principal stress and fracture pressure were higher, poisson＇s ratio was larger, the shear modulus was small, and the principal stress orientation was deflected. So the mechanical characteristics can be used to establish the formation or existence of casing damage area in reservoir section. Higher fracture pressure, bigger poisson＇s ratio, smaller shear modulus, and greater differences in stress are internal cause of casing damage in N2 index bed. Plane stress differences between regions are standard parts of the external impetus of casing damage. The rock mechanical characteristics which bigger poisson＇s ratio, smaller shear modulus, fracture pressure is higher, and so on, are the internal causes of casing damage in reservoir section. The changes of geologicalstress field and formation-pressure-field are the external causes of casing damage in reservoir section. The casing damage in reservoir section is the result of the effect of internal and external causes.