Study On Cement Slurry System For Tight And Low Permeability Reservoir In Ordos Basin

The tight low permeability reservoir area in southern Ordos Basin has achieved certain effects by means of horizontal well drilling,fracturing and other methods.However,because of the complex formation structure in this block,such as low-pressure and easy-leakage,leakagae is extremely easy to occur during cementing.In this paper,chemical nitrogen foam cement slurry is studied to solve the easy-leakage problem that during cementing in Quaternary and Zhidan Group formation in the upper vertical section of tight and low-permeability reservoirs in southern Ordos Basin.In view of the cementing problem caused by fracture development in Yanchang formation of lower horizontal well section,the low-density,high-strength and toughness cement slurry was studied,and the matching cementing process parameters were designed and optimized.In this paper,based on the characteristics of nano materials for the stability enhangcement of foam,a new method for improving the stability of foamed cement slurry by nano liquid silicon was studied.The effects of the nano liquid silicon were evaluated,and its optimal addition was optimized.Cooperating with plugging pre-fluids,a"plugging pre-fluids+high performance chemical nitrogen foam cement slurry"system was established for the upper vertical well section,aiming at the problem of easy-leakage in low pressure and fractured formations.For the lower horizontal section,through optimizing the addition of elastoplastic mitigating materials,toughening fiber material,admixture,epoxy resin and nano-liquid silicon,combining with the performance test of cement slurry,the epoxy resin-nano liquid silicon cement slurry was developed to achieve the goal of low-density,high-strength and toughening.The results showed that:(1)nano stabilizer NS-35 compounded with foam stabilizer can enhance the foam stability which could help reduce the density of cement slurry effectively;(2)NS-35 has good compatibility with cement slurry,and high performance chemical nitrogen foam cement slurry with density of 0.80-1.02 g/cm~3 was developed in combination with foam stabilizer,aerating agent and admixture;(3)Elastoplastic materials can help to lower the density of cement slurry and improve the plastic deformation of cement slurry;(4)Epoxy resin and nano-liquid silicon can form a dense structure through the curing cross-linking reaction and filling effect of particles,which improves the compressive strength and toughness of cement stone;(5)An epoxy resin-nano liquid silicon cement slurry with a density of 1.65 g/cm~3 is constructed to achieve the goal of low density,high strength and toughening;(6)The cementing fluids have good compatibility with each other wellbore working fluid,and the cementing process parameters are optimized by taking Honghe 198 well as a reference.