水平井的表皮因子

Skin factor of horizontal wells

水平井在开采低品质油气资源方面具有一定的优势,但已建立起来的水平井产量计算公式很少考虑油井的表皮因子,因而产量预测偏差较大。根据等值渗流阻力法,推导了水平井的产量计算公式,该公式引入了油井的2个表皮因子:地层伤害表皮因子和地层改善表皮因子。地层伤害表皮因子是由钻井完井过程中的泥浆侵入所致,而地层改善表皮因子是由酸化压裂等增产措施所致。二者对水平井产能的影响有所不同,地层伤害表皮因子对水平井产能的影响较小,钻井完井过程中可以不考虑储层的保护问题;地层改善表皮因子对水平井产能的影响较大,增产措施是提高水平井产能的有效方法。

Horizontal wells have advantages to vertical wells in developing low quality petroleum resource. However the conventional production rate equations of horizontal wells seldom take into account the skin factor of wells, with which production rates of horizontal wells can not be well predicted. Based on the equivalent flow resistance theory, a new production rate equation of horizontal wells was derived in this paper with the skin factor. Two skin factors are introduced into the new equation, which are formation damage skin factor and formation improvement skin factor. The formation damage skin factor is resulted from mud intrusion in drilling and completion of wells, while the formation improvement skin factor is resulted from stimulations of wells such as acidizing and fracturing. The two factors have different effects on production rates of horizontal wells. The formation damage skin factor affects production rate of horizontal wells to a quite small extent, however the formation improvement skin factor to a quite great extent. So the formation protection in drilling and completion of horizontal wells are not necessary, while the stimulations are effective methods to enhance the productivity of horizontal wells.