Process for preparing drilling fluid for preventing polycrystalline diamond compact (PDC) bit balling

Abstract

The invention relates to a process for preparing drilling fluid, in particular to a process for preparing the drilling fluid for preventing polycrystalline diamond compact (PDC) bit balling. The process comprises a construction process and a dosage formula of treating agents and is characterized in that: according to the dosage formula, the treating agents are prepared by mixing clear water polymer original slurry, poly anionic cellulose (PAC), calcium carbonate (QS-4), carboxymethyl starch (CMS), sulfonated phenolic resin(SMP-2), water dispersible cation emulsified asphalt powder (SFT-1), sodium chloride(NaCL) and sodium formate (WT-1) in a mass ratio of 1,000:2-3:30-40:20-30:2-3:1.5-2:50-100:20; and the construction process comprises the following steps of: according to a circulation circle, uniformly mixing a coating agent PAC, a filtrate reducer CMS, a salt and high-temperature resistant filtrate reducer SMP-2 and an anti-sloughing lubricant SFT-1 for 12h at first; adding QA-4, NaCL, WT-1 into the mixture and uniformly mixing the mixture; and regulating the mixture to have a density Rho of 1.06 to 1.10g/cm<3>, a funnel viscosity T of 38 to 45s and an API water loss FL of 4 to 6ml. The process has the advantages of effectively preventing the balling of a sticking bit and a PDC bit at a lower curved section, reducing a frictional resistance and a torque, eliminating a sticking phenomenon, improving a mechanical drilling rate and ensuring downhole safety.

Description

technical field [0001] The invention relates to a drilling fluid preparation process, especially a drilling fluid preparation process for preventing PDC bit balling. The process is suitable for the prevention of drill bit balling in the "shuangshi layer" formation of Sulige gas field, and belongs to oil drilling field. technical background [0002] The "Shuangshi Formation" of the Sulige Gas Field belongs to the Permian system, and the burial depth of the formation is about 3000m to 3600m. The mudstone content in the formation is high and easy to hydrate and disperse, which greatly increases the content of mud or solid phase in the wellbore and is adsorbed on the surface of the drill bit. At the same time, this well section is just in the transition from clear water polymer to completion fluid, and the performance of the drilling fluid is poor immediately after conversion, such as large water loss, thick filter cake, poor inhibition, and poor lubrication performance. influe...

AI Technical Summary

Problems solved by technology

However, the polysulfide drilling fluid system itself has limitations, such as poor inhibition, high solid content, rapid increase in specific gravity, poor drilling fluid inhibition, and cannot control the hydration and dispersion of shale; the solid content and viscosity shear are too high, and the drilled Cuttings are difficult to remove and are easily adsorbed on the surface of the drill bit; the specific gravity of the drilling fluid is high, the water loss is large, and an excessively thick rough mud cake is easily formed; the lubrication performance is poor, and an effective protective film cannot be formed on the surface of the drill bit. It is easy to be adsorbed on the drill bit, resulting in the mud bag of the PDC bit, which seriously affects the speed-up of the Sulige gas field and becomes a technical bottleneck restricting the speed-up

Especially in the construction of horizontal wells, the mud bag problem is more prominent. There have been downhole accidents in many wells where the PDC bit cannot be used and the cone bit has lost the cone due to the serious mud bag of the "double rock layer" bit.

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