碱敏损害是塔里木盆地东河塘构造东河1井减产的主因

利用岩相学分析手段,结合东河1井(塔里木盆地一口重要的油气发现井)减产的主要原因是高pH值盐水压井液造成的碱敏损害,揭示出:以高岭石为主,伊/蒙间层矿物含量低,间层比亦低的粘土矿物微结构属稳定类型,从而决定了储层潜在损害必以碱敏为主。这与实验和矿场试验结果恰好吻合。碱敏损害的机理包括:粘土断键处电性变化而使微结构失稳、阳离子交换、新矿物相生成等。由此提出了相应的缓解碱敏损害的技术措施。

Alkali Sensitivity Damage : A Critical Factor Causing Drastic Decrease in OilProduction for Well Donghe 1 in Tarim Basin

Although alkali sensitivity of reservoirs has been discovered for several decades, it has not been paid much attentions by petroleum engineers in China. It began to attract considerations from the petroleum engineering sector when the fact that alkali sensitivity damage from salted kill fluids with higher Ph was recognized to be a critical factor causing drastic decrease of oil production for well Donghe 1 which was an important discovery well in Tarim Basin occured. Petrographic analysis indicates that kaolinite kominates clay minerals while the content of swelling clays is much lower than that of kaolinte. Most of the clay microstructures are relatively stable. These facts determine that the critical factors of potential damage must be alkali sensitivity. Core flow tests show that alkali sensitivity is the most severe sensitivity among flow rate, fresh water, HCL acid, salted water sensitivity. Simulations of working fluid - core interations proved that working fluids with high Ph (higher than 9) cancause decrease of core permeability in a great magnitude. Analysis of operations and well test information further provide evidences to verify that salted kill fluid with high pH is a critical factor for the decrease of oil production. Mechanisms of alkali sensitivity include changes of electric property on the edge of clay crystals that lead to failureof clay microstructures, cation exchange, and deposition of new minerals. It is a curious coincidence for the example given in this paper that salted kill fluid with high PHseriously damages the reservoir; at the same time,the most severe factor of potential damage is also alkali sensitivity. Finally, a few techniques to alleviate damages from alkali sensitivity are presented.