A Novel Multifunctional Bionic Fuzzy-Ball Drilling Fluid

Abstract

The difficulties during the exploration and development of the reservoirs which are low pressure-permeability, low pressure fractured hydrocarbon or energy depleted put multi-requirements on drilling fluid, which include the capacity of inhibiting and sealing to avoid down hole losses and formation caving in the situation where different pressure coefficients exist in the same open hole, good compatibility with underbalanced drilling fluid such as air, mist, foam etc, good solids-carrying capacity and formation damage control according to varies kinds of well completion in different types of well like vertical, horizontal or multilateral well. Thus a novel multifunctional bionic fuzzy-ball drilling fluid was invented under the auspice of National Key Project. The density of the fluid which is solid free can reach to 0.8~1.0 g/cm3 with conventional drilling equipments. Also, its density can be above 1.0 g/cm3 by adding inert weighting additives to adapt to near-balanced or under-balanced drilling. Good sealing ability can avoid down hole losses, formation caving in opening and low-pressure layers above 1000m. The ratio of yield value and plastic viscosity can be above 1.0 Pa/mPa·s, which makes good performance in hole cleaning under low pump delivery with conventional drilling equipments. Being compatible with air, it can be used in water producing, sloughing formation and completions without converting to other types of drilling fluid system. Bionic fuzzy-ball drilling fluid has been used in more than 10 wells, which have the problems such as water production, formation caving and severe losses, and applied to air drilling. The field applications of bionic fuzzy-ball drilling fluid can be demonstrated by introducing the “U” shape horizontal well DFS-02-H2, multilateral well FL-H2-L, artesian flowing and formation caving well J35, air drilled well CLY22 and low pressure gas well Mo 80-C1.