水平井眼轨迹对气井出砂趋势及工作制度的影响

HOW HORIZONTAL WELL TRAJECTORY AFFECTS THE SAND-PRODUCING TENDENCY AND WORKING SYSTEM OF A GAS WELL

出砂是影响油气井正常生产的重要因素之一。借助FEPG有限元程序自动生成平台,建立了三维应力场弹塑性地层出砂模型,并运用有限元法计算分析了不同轨迹的裸眼井井壁周围的有效塑性应变分布规律及出砂趋势,研究了气藏压力衰竭对完井方式的影响。研究表明,水平井眼轨迹对出砂有重要的影响,同一地应力环境下向不同方位延伸的水平井在投产时应该采取不同的生产压差和不同的生产制度,水平井眼轨迹对出砂的影响程度随着3个地应力差异的增大而加剧。气藏压力衰竭对井壁的稳定性和出砂趋势都有重要影响。随着气藏压力的衰竭,井壁稳定性将变得越来越差,最终导致井筒出砂。因此,对气井完井不仅应该考虑到气藏开发初期地层的稳定性状况,而且还应该考虑到气藏压力衰竭后可能出现的井壁失稳问题。

Sand production is one of the important factors that have influence upon the production of oil/gas well. This paper makes use of FEPG finite element program to generate platform automatically and establish a sand production model in a 3D stress field for elasto-plastic formations. Meanwhile, it is computed and analyzed the distribution of effective plastic strains and the sand production tendency around the wellbore of open holes with different trajectories, and meanwhile the relationship is discussed between the pressure depletion and the completion method. The study results show the horizontal well trajectory is related with sand production. Under the same earth stress, different production pressure differential and production system should be adopted for horizontal wells extending in different directions when putting into production. The effects of horizontal well trajectory on sand production will aggravate with the increase of the differences among the three stresses. The study also demonstrates the gas reservoir pressure depletion has played an important role in well stability and sand production tendency, the well stability will get worse when gas reservoir pressure depleted, which induces sanding eventually. Therefore, for gas well completion, the formation stability should not only be considered at an early stage of development, but also the possibility of well instability problems be considered when gas reservoir pressure is becoming depleted.