带形油气藏中水平井方向优选研究

在对比分析齐成伟导出的带形油气藏中纵向双分支水平井和横向水平井拟三维产能公式的差异后,提出了"纵横阻力比"的概念。在笛卡尔直角坐标系中,以穿透比为X轴,以长宽比为Y轴,以纵横阻力比为Z轴,可以绘出纵横阻力比曲面图。观察纵横阻力比曲面发现其只在局部是光滑的,在长宽比较大时呈现出急剧的震荡。同时,得出重要结论——在带形油气藏中,横向水平井的产能远小于纵向水平井。分析齐成伟导出的带形油气藏中裂缝外渗流场之复势公式,认识到约有3/4的石油将流入纵向水平井两端,造成水平井中部石油难以采出。当油气藏长宽比较大,需要采用纵向双分支水平井时,两分支之间的石油可以通过交替关闭一个分支来采出,但每条分支生产段中部的石油仍然难于采出。于是,得出另一重要结论——在带形油气藏中,纵向水平井的采收率远小于横向水平井。

Research on Horizontal Well Orientation Optimization Based on Productivity and Recovery in Ribbon-shaped Reservoirs

The concept of longitudinal-transverse resistance ratio is proposed on the basis of contrastive analysis of differences in pseudo 3-D productivity formulae,derived by QI Cheng-wei,of longitudinal bilateral horizontal wells and a transverse horizontal well in ribbon-shaped reservoirs.A surface of longitudinal-transverse resistance ratio can be plotted in Cartesian coordinate system,with X axis being the penetration ratio,Y axis the length-width ratio,and Z axis the longitudinal-transverse resistance ratio.It is observed that the said surface is only locally smooth and exhibit sharp fluctuations where length-width ratio takes on large values.In addition an important conclusion is arrived at that in ribbon-shaped reservoirs productivity of the transverse horizontal well is lower by a large margin in comparison with that of longitudinal wells.A detailed study of complex potential formulae,derived by QI Cheng-wei,of extra-fractural seepage fields in ribbon-shaped reservoirs,led to the observation that 75% of petroleum will flow into two ends of the longitudinal well,causing difficulties in extraction in the region around the central part of the production segment.In cases where length-width ratio is of large values and it is necessary to employ longitudinal bilateral wells,the extraction can be accomplished by means of alternate shut-off of branches,but extraction is still of substantial difficulty in the region around the central part of the producing branch.The conclusion therefore is that the recovery in longitudinal horizontal wells is much lower in relation to the transverse horizontal well in ribbon-shaped reservoirs.