井眼测量误差椭球最小间距计算方法

A calculation method of minimum distance between wellbore survey error ellipsoids

随着丛式井和加密井在油田的广泛应用,对井眼防碰分析提出了更高的要求。井眼分离系数是防碰分析的一个常用指标,然而不同误差椭球分离距计算方法导致结果差异较大,为此提出测量误差椭球最小间距计算新方法,以更好地满足应用需要。在坐标变换及误差椭球计算基础上,推导了中心向量法误差椭球分离距计算公式,进而应用最优化理论求解了两误差椭球最小间距,并研究了快速求解策略,可精确、快速地计算井眼分离系数。算例分析表明,与其他计算方法相比,新方法能更好地指导井眼防碰风险评价工作,在丛式井设计和定向钻井中具有应用价值。

With the wide application of cluster wells and infill wells in oilfields,higher requirements are put forward for the wellbore anti-collision analysis.Wellbore separation factor is a common index for anti-collision analysis.However,different calculation methods of the distance between wellbore error ellipsoids lead to great differences in results,so that a new method was presented to calculate the minimum distance between wellbore survey error ellipsoids to satisfy the application requirements.Based on the coordinate transformation and error ellipsoid calculation,the formulae for calculating the distance between wellbore error ellipsoids were derived by the center vector method;the minimum distance between wellbore error ellipsoids was further solved using the optimization theory;a rapid solution strategy was also studied to calculate the separation factor accurately and rapidly.The case analysis show that the new method can guide the wellbore anti-collision risk assessment better than other calculation methods,which has application value in the cluster well design and directional drilling.