歧口凹陷沙一下亚段页岩油井增产措施地质影响因素分析

Geological influence factor analysis of stimulation treatment on shale oil wells of the lower first member of Shahejie Formation in Qikou Sag

歧口凹陷沙一下亚段混合质页岩层系发育,孔隙结构主要为微孔-介孔,其中以灰质混合页岩孔隙结构最为发育,含油性以重质稠油为主。经过措施改造后,油井普遍达到工业油流,但尚未明确影响产能的地质因素,对此需要在该区开展相关研究,指导类似油井措施改造增产。根据岩石物性、岩石岩性,以及裂缝发育程度、地层压力和断裂规模、构造形态和曲率、电性参数等数据,总结出“自然产能井”“酸化有效果井”“压裂有效果井”“酸压有效果井”所对应的地质特征,以此来指导措施改造方式的选取。研究结果表明:(1)该区孔隙度低于15%、渗透率低于0.41 mD的页岩层系需经措施改造提产;(2)“自然产能井”以邻近断裂、裂缝较为发育的灰质混合页岩、长英质页岩为主,D值(井到断裂距离与垂直断距比值)普遍小于1,断裂影响较为明显,且构造曲率较大;(3)“酸化有效果井”以灰质混合页岩、云质混合页岩为主,总体上灰质含量较高,D值2.8~7.9,断裂对地层改造程度较弱,构造曲率中等,电性参数ΔGR普遍大于20 API;(4)“压裂有效果井”的D值为1.2~5.2时,以裂缝发育较差的云质混合页岩、长英质页岩为主,D值大于16时,断裂的影响极其微弱,以不发育裂缝的灰质混合页岩为主,“压裂有效果井”对应的构造曲率较小,电性参数ΔGR普遍小于20 API。基于不同产能井的地质因素影响分析,归纳提出“自然产能井”“酸化有效果井”“压裂有效果井”“酸压有效果井”适用的地质环境,指导该区新完钻井采取相应增产措施,改造后达到了工业油流产出标准,有效地提高了油气产量,对油田页岩层系提产具有积极的作用。

In the Qikou Sag of Bohai Bay Basin,the hybrid shale layer is developed,and the pore structure is mainly microporous and mesoporous,among which the pore structure of the calcareous hybrid shale is the most developed,and the oil content is mainly heavy crude oil.After the reconstruction of measures,the oil wells generally reach the industrial oil flow,but the geological factors influencing the productivity are not clear,so it is necessary to carry out relevant research in this area to guide the stimulation of similar oil wells.According to the data of rock physical property,rock lithology and fracture development degree,formation pressure and fracture scale,structural morphology and curvature,electrical parameters,etc.,the corresponding geological characteristics of"natural productive wells""acidizing effective wells""fracturing effective wells"and"acid fracturing effective wells"are summarized to guide the selection of transformation methods.The results are obtained in four aspects.First,shale layers with porosity lower than 15%and permeability lower than 0.41 mD in this area need to be reformed to improve production.Second,"natural productive wells"are dominated by gray mixed shales and felsic shales with relatively developed adjacent faults and fractures.The D value(ratio of the distance from well to fault to vertical fault distance)is generally less than 1,and the influence of faults is obvious and the structural curvature is large.Third,acidizing effective wells are mainly composed of calcareous hybrid shale and dolomitic hybrid shale,with high calcareous content in general,D value of 2.8-7.9,weak degree of formation transformation by faults,medium structural curvature,and electrical parameterΔGR generally greater than 20 API.Fourth,when the D value of"fracturing effective wells"is 1.2-5.2,dolomitic hybrid shale and felsic shale with poor fracture development are the main ones.When D value is greater than 16,the influence of faults is very weak,and the calcareous hybrid shale without fractures is the main one.The structural curvature corresponding to the well with effective fracturing is small,and the electrical parameterΔGR is generally less than 20 API.According to the analysis of geological factors of different productive wells,the geological environment suitable for"natural productive wells""acidizing effective wells""fracturing effective wells"and"acid fracturing effective wells"is put forward to guide the newly completed drilling in the area to take stimulation treatment,and after the transformation,the industrial oil flow standard is reached,and the oil and gas production is effectively increased,which has a positive effect on the production of shale layers in the oilfield.