致密油水平井出砂机理

大庆油田A致密油试验区10口水平井投产16个月后,就有3口井的砂柱到井口,致密油水平井出砂问题日益突出。通过探讨致密油水平井出砂机理,研究了适合大庆油田的致密油水平井出砂临界压差计算方法。依据出砂临界压差和衰竭开发阶段性渗流特征,建立了致密油水平井防砂方案。通过治理A致密油试验区B水平井出砂问题,并以压力恢复试井资料和生产数据验证了致密油水平井出砂机理。结果表明:含水率升高是致密油水平井出砂的主要原因,含水率升高时,远井地带泥质填充物膨胀堵塞地层,近井地带泥质填充物松动后与裂缝壁面游离砂随流体进入井筒造成出砂;生产压差大于出砂临界压差时将造成裂缝壁面破碎而出砂。致密油水平井采取间歇采油制度并以小于临界生产压差的压差生产后,有效控制了出砂量,延长了油井寿命。

SAND PRODUCING MECHANISM FOR THE HORIZONTAL WELLS IN THE TIGHT OIL

The sand columns of 3 wells were arrived at the wellhead after 16-month production of 10 horizontal wells in the tight oil test area A of Daqing Oilfield,and moreover the problem of the sand production of the horizontal well in the tight oil was increasingly prominent.Through the exploration and discussion of the sand producing mechanism of the horizontal well in the tight oil,the calculating method suitable was studied for the critical pressure drawdown of the sand production for the horizontal wells in the tight oil of Daqing Oilfield.According to the critical pressure drawdown and seepage characteristics for the sand production at the stage of the failure development,the sand control program of the horizontal wells in the tight oil was established.The sand production problem of the horizontal well B in tight oil test area A was governed,and the sand producing mechanism of the horizontal well in the tight well was verified by the pressure build-up test data and production data.The results show that the increase of the watercut is the main cause for the sand production of the horizontal well,and when the watercut is increased,the expanded argillaceous filler in the far wellbore area blocks the formation,while the argillaceous filler in the near wellbore area is loosened and then enters the wellbore in the form of the free sand on the fracture wall with the fluid,thus results in the sand production;the fracture wall would be broken and produce the sand when the production pressure drawdown is greater than the critical drawdown pressure.The horizontal well in the tight oil adopts the intermittent oil production system and produces with the pressure difference less than the critical pressure drawdown,and then the sand production rate is effectively controlled,thereby the production life of the oil well can be prolonged.