Research And Application Of Low-toxic Oil Based Drilling Fluids In Shale Oil & Gas Drilling

In recent years,With attenuation of conventional oil and gas resource,many countries have turned their highlight of exploration and development to be focused on unconventional oil and gas resource.Our country has started to do focused research of unconventional resource since the beginning of this century;especially commercial discovery has been achieved in some oildoms after putting into a large number of human resources and material resources in recent years.Stability and environmental protection of borehole wall are two of major challenges that restrict domestic unconventional exploitation.Due to that geologic structure of domestic unconventional resource is quite different from abroad and formation anisotropism and aeolotropism is stick out and brittle mineral content of mineral composition is high,moreover,it has a certain character of hydration dispersion that leads borehole cannot go forward a certain length along formation,which incurs that it is difficult for unconventional oil-gas well to reach commercial exploitation.Rejection capability of Oil-based drilling fluid is strong,which can solve the problem that borehole wall stability is inferior,nonetheless,arene content of diesel is high that it will seriously corrode equipments and constructors will be easily injured,what's more,post-disposal for cuttings is difficult that construction environmental protection will be hard to maintain.This paper carries out researches of low toxicity oil-based drilling fluid based on oil-based drilling fluid developed in Shengli oilfield,in accordance with optimization of base drilling fluid and study evaluation of formula laboratory,basic formula of low toxicity oil-based drilling fluid is to be determined,meanwhile,anti-fouling performance has been evaluated and low toxicity oil-based drilling fluid technology is being formed and improved as per using in Boyeping 2 well,Yi 173-5HF well and Nanye 1 well.After being proven by test of those 3 wells,anti-pollution capacity of low toxicity oil-based drilling fluid is strong in drilling process and trip in/out and completion work go smoothly and construction friction is small that efficiently lower equipments' load,which grantees the construction has been completed successfully.In accordance with comparison and analysis the four indexes of similar type wells in similar block,wellbore quality,average ROP,completion period and drilling fluid materials consumption in single month,wellbore quality of using low toxicity oil-based drilling fluid is good,enlarging rate is less than 2%,drilling rate can be enhanced 2 times,completion period can be saved 1/3 and drilling cost is synthetically reduced.This type of drilling fluid has solved the problem of environmental protection for unconventional resource exploration and development and borehole wall stability in Shengli oildom,and it also can be taken as reference and has guiding significance to other complex formation and unconventional resource exploration in other oildoms.