黄骅坳陷纹层型页岩油富集与提产提效关键技术

Enrichment characteristics and key technologies for production and efficiency enhancement of laminated shale oil in Huanghua Depression in Bohai Bay Basin

渤海湾盆地黄骅坳陷具有形成纹层型页岩油的有利条件,其古近系发育孔二段、沙三段和沙一段3套湖相纹层状页岩,叠合面积约为2400km^(2),累计最大厚度超过1200m,计算纹层型页岩油资源量是常规油资源量的1.2倍,勘探开发潜力巨大,但如何实现效益开发仍面临一系列难题。基于5口井701m页岩岩心开展的52项22640块次的分析联测,结合116口直井测井、录井资料,提出断陷盆地纹层型页岩油富集,平面主要分布于前(扇)三角洲—半深湖亚相,纵向主要形成于中等热演化阶段并以滞留油形式富集于基准面上升/下降(T/R)旋回转换带,建立了3类8因素的页岩油有利区与富集层的定量评价标准,有效指导了纹层型页岩油“甜点”评价优选;通过37口页岩油水平井不同开发方案、不同类型压裂方式、不同排采工艺等现场试验,提出水平井井距300m、水平段段长2000m为效益最优水平井布井方式,单点密切割缝网体积压裂可大幅提升单井产量和最终采收量(EUR),优化形成了小油嘴控压降水、大油嘴提液防堵、中油嘴稳定自喷、小泵深抽长期生产的“四步法”排采方式,实现了页岩油的高产稳产。以纹层型页岩油富集认识和关键提产提效技术为指导,实现了单井首年最高累计产油超1×104t、EUR超3.5×104t,达到了油价50美元/bbl下的效益开发,展现了我国东部断陷盆地页岩油的良好发展前景。

Huanghua Depression in Bohai Bay Basin has favorable conditions for the formation of laminated shale oil.The three sets of lacustrine laminated shales in the second member of Kongdian Formation,third member of Shahejie Formation and the first member of Shahejie Formation have a superimposed area of about 2400km2,the maximum cumulative thickness of about 1200m,and the calculated shale oil resource volume of 1.2 times that of conventional oil resources,showing great exploration and development potential.However,the benefit development still faces a series of difficulties.By conducting 52 items of joint experiments and tests on 22640 shale samples(701m core)collected from five wells,and analyzing mud logging and wireline logging data in 116 vertical wells,the distribution of the laminated shale oil is identified,which is enriched in(fan)predelta to semi-deep lake subfacies laterally and in the transition zone of the base level T/R cycle vertically in the form of retained oil generated by source rocks in the medium thermal evolution stage.In addition,the quantitative evaluation standard for three types of shale oil favorable areas and enrichment layers is established by eight factors,which effectively guides the“sweet spots”evaluation and selection of the laminated shale oil.Moreover,the field tests of different development schemes,different types of fracturing methods,and different production regimes are conducted in 37 shale oil horizontal wells,which indicate that the optimal horizontal well placement mode can be achieved by using horizontal well spacing of 300m and horizontal section length of 2000m,single-point densely-cutting network volume fracturing enables to greatly improve the production and EUR of single well,as well as the optimally formed“four steps”shale oil well production method,namely,pressure control and water production by small choke,liquid lift/production and blockage prevention by large choke,steady natural flow by medium choke,and long-term production by deeply-set small pump,supports to achieve the high and steady shale oil production.Guided by understanding of enrichment law and key technologies for production and efficiency enhancement of the laminated shale oil,major breakthrough has been made with the highest cumulative oil production of 1×104t in the first year and EUR of over 3.5×104t of a single well,achieving the benefit development at an oil price of USD 50$/bbl,which shows promising development prospect of shale oil in fault basins in eastern China.