Clay-free low-density oil-based drilling fluid

Abstract

The invention relates to drilling liquid for use in the drilling process of oil exploration wells and production wells and belongs to low-density oil-based drilling fluid. The drilling fluid overcomes the drawbacks of serious pollution and strong Jamin effects of the conventional oil-based drilling fluid in hypotonic and water sensitive reservoir strata. The drilling fluid is characterized by containing low-density base oil, oil thickener, oil swelling agent, oil dispersible particle calcium carbonate, calcium oxide and oil soluble high-temperature-resistance fluid loss additive. The drilling fluid does not contain any water phase, the breaking voltage of the drilling fluid is high, the viscosity of the drilling fluid is proper, and the filtration is small (all filtrate is oil). The drilling fluid has the characteristics of high electrical stability, high temperature resistance, high water, soil and salt pollution resistance, excellent emulsification effect at high temperature and the like. The stabilization time of the drilling fluid can reach 20 to 40 hours.

Description

technical field [0001] The invention designs a drilling fluid used in the drilling process of petroleum exploration wells and production wells, which belongs to the low-density oil-based drilling fluid system. technical background [0002] At present, in the process of oilfield exploration and development, many large oilfields at home and abroad have entered the later stage of development, and some low-pressure and low-permeability reservoirs have been put into development one after another. Exploration and development of these reservoirs are difficult and require high drilling fluid density. During the drilling process, drilling fluid is essential. It can carry and suspend cuttings, stabilize the well wall and balance the formation pressure, cool and lubricate the drill bit and drilling tools, and transmit hydrodynamic force. The performance of the drilling fluid directly affects the quality of the well and the drilling speed. In the process of drilling in low-pressure, l...

AI Technical Summary

Problems solved by technology

Due to many shortcomings of aerated drilling fluid or foam drilling fluid, and its compressibility, the pulse signal attenuation is serious, and the use of MWD is limited when drilling horizontal wells and extended-reach wells.

In addition to the above disadvantages, foam drilling fluid cannot be used in areas with strong water sensitivity

In the drilling process of low-pressure and low-permeability reservoirs, if the conventional oil-based drilling fluid is used, the emulsified water droplets contained in it will often cause serious Jamin effect in the reservoir; in order to maintain the stability of the water-in-oil emulsion, a A large number of emulsifiers will cause the rock surface to change from hydrophilic to oil-friendly, causing damage to the reservoir; it is difficult to adjust the water activity of the drilling fluid to balance the activity of water in different easily collapsed formations at any time, so it is impossible to ensure Collapsing formation does not cause hydration to destabilize the borehole wall

At the same time, in the current all-oil-based drilling fluid system, most of them contain organic soil and lipophilic colloid, and the particle size of these substances is between 1 and 10 μm, which is equivalent to the pore throat size of the reservoir. At the same time, these materials also have Strong deformability, therefore, the presence of these materials can lead to more severe contamination of low-permeability reservoirs