鱼骨分支井布置方案及井眼轨道设计——以玛湖凹陷下三叠统百口泉组为例

Arrangement scheme and well trajectory design of fishbone branch wells:taking Baikouquan Formation of lower triassic in Mahu Depression as an example

准噶尔盆地玛湖凹陷百口泉组为超深、特低渗、中等孔隙度致密砂砾岩油藏,区块内主要采用“水平井+体积压裂”的开发方式,取得明显的开发效果。同时,新疆油田也具有开发鱼骨分支井的经验。鱼骨分支井的布置方案决定了鱼骨井的产油能力,但同样决定了钻井的难易程度和成本消耗。在满足鱼骨井布置方案要求的同时,降低钻井风险和成本尤为重要。所以,尝试分析将鱼骨分支井作为玛湖油藏新开发思路的可行性,通过建立产量预测模型,模拟不同布置方案对鱼骨井产油能力的影响。此外,以各布置方案为基础,设计一系列鱼骨井分支井眼轨道,分析不同造斜率对滑动钻进工况下钻柱所受摩阻以及分支井眼各分段长度的影响。研究表明,相较于常规水平井,鱼骨分支井能有效地提高单井产量,其中增大分支井眼长度和分支数最为明显。采用6°/30m和7°/30m的造斜率在能够保证多数鱼骨井实钻井眼能够达到设计指标的同时,减少分支井眼扭方位段长度和钻柱所受摩阻,进而可降低分支井眼的钻进成本和钻井风险。

Baikouquan Formation in Mahu Oilfield depression of Junggar Basin is a super-deep,ultra-low permeability,medium porosity dense breccia reservoir,the development method of"horizontal well+volume fracturing"is mainly adopted in the block,and obvious development effect has been achieved.At the same time,Xinjiang Oilfield also has the experience of developing fishbone wells.The layout scheme of fishbone well determines the oil production capacity,but also determines the drilling difficulty and cost consumption.It is particularly important to reduce drilling risk and cost while satisfying the requirements of fish-bone well layout.Therefore,this paper attempts to analyze the feasibility of using fishbone well as a new development idea of Mahu reservoir,and simulate the influence of different layout schemes on the productivity of fishbone wells by establishing production prediction model.In addition,a series of branch hole trajectories of fishbone wells are designed on the basis of various layout schemes,and the effects of different build-up rates on friction of drill string under sliding drilling conditions and the length of each section of branch hole are analyzed.Analytical results show that compared with conventional horizontal wells,fishbone well can effectively improve single well production,and the increase of branch wellbore length and branch number is the most obvious.Using 6°/30 m and 7°/30 m build-up rates can ensure that most of the fish-bone wells can meet the design targets,reduce the length of twist azimuth section of branch wells and the friction of drill string,thereby reducing the drilling cost and drilling risk of branch wells.