Modified composite barite for drilling fluid

Abstract

The invention discloses modified composite barite for a drilling fluid. The barite is prepared from composite barite, a modifier sodium hexametaphosphate, an acrylic copolymer, octylphenol ethoxylate-30 and polyethylene glycol 400. According to the modified composite barite, on the basis that ultrafine barite and baryto calcite are compounded, an acrylic copolymer hyperdispersant is prepared fromsodium hexametaphosphate and phthalic anhydride, acrylic acid and n-butyl alcohol as monomers to improve the surface property of a weighting agent, furthermore, surfactants octylphenol polyoxyethyleneether-30 and polyethylene glycol 400 are used as auxiliary materials to further enhance the hydrophilic dispersion performance, and thus the modified composite barite is prepared, the modified composite barite is suitable for a water-based drilling and completion fluid, the suspension property is excellent, and the density reduction rate of a weighted drilling fluid system is lower than 3%; the acid solubility is greater than or equal to 45%; the viscosity coefficient of a drilling fluid system filter cake is lower than that of conventional barite by 30% or above; and the apparent viscosity change rate before and after the calcium sulfate is added is less than or equal to 3mPa*S.

Description

technical field [0001] The invention belongs to the field of drilling fluid in petroleum and natural gas and geological exploration and development, and discloses a modified composite barite for drilling fluid. Background technique [0002] In oil and gas exploration and development drilling, weighting agent is an indispensable additive in drilling fluid. Its main function is to add to drilling fluid to increase the density of drilling fluid, to stabilize the well wall, to balance the formation pressure, and to prevent blowout and blowout out of control accidents. purpose of occurrence. The weighting agent itself has high density, low abrasiveness, and is easy to crush. It is generally prepared by grinding and processing inert substances that are insoluble in water. interaction. Currently commonly used weighting agents mainly include barite powder, limestone powder, iron ore powder, ilmenite powder, and galena powder. Among them, limestone powder is suitable for use in pro...

AI Technical Summary

Problems solved by technology

At present, the domestic conventional barite also has some shortcomings: ①In the case of high underground pressure, it is necessary to increase the proportion of mud, and adding barite powder to the drilling fluid is an effective measure to increase the proportion of mud

The barite fineness used in the drilling fluid should generally be above 325 meshes. If the barite fineness is not enough and the drilling fluid structure is not strong, it is easy to separate and settle at the bottom of the circulation tank; in addition, the drilling fluid is treated on-site using a centrifuge When the equipment separates the harmful solid phase, due to the limited equipment conditions, a certain amount of barite will be separated together with the harmful solid phase, resulting in a decrease in density, and it is necessary to add barite again

②At present, when most barites on the market are added to the mud, the viscosity and shear force of the aggravated drilling fluid will be greatly increased, which will not only lead to a decrease in the rheological properties of the drilling fluid, but also cause If the pump pressure is too high, the drilling fluid is more likely to be invaded by gas, which increases the chance of inducing blowout

As the density increases, the amount of barite used increases, and this situation becomes more serious, making it difficult to maintain the performance of drilling fluids

In order to restore the good rheological properties of the high-density drilling fluid after being aggravated, it is necessary to add a treatment agent for treatment, and the viscosity and shear force of the high-density drilling fluid will decrease after treatment, which will lead to the precipitation of part of the barite, causing reduction in mud density

Not only was a large amount of barite and drilling fluid treatment agent wasted, but also it was difficult to achieve stable and high-quality performance, and it would also induce downhole complex situations such as blowout, leakage, collapse, and sticking

③During the drilling process, especially when drilling in the reservoir, since the reservoir fractures and seepage channels are well developed, the barite in the drilling and completion fluid will inevitably invade the fractures and seepage channels and remain in them. Accumulation will cause blockage of oil and gas seepage channels, resulting in a decrease in oil and gas production, and barite is an inert substance, which requires the addition of chelate and other blocking agents for blockage removal and flowback, which is expensive and ineffective

[0004] At present, in order to reduce the settlement of barite, increase the dispersibility of barite in drilling fluid, and reduce the impact of barite on the reservoir, although some relevant researchers have conducted research on the modification of barite, although barite The settlement problem in the drilling and completion fluid has been improved, but the hydrophilic barite will increase the migration resistance of oil and gas, which is not conducive to reservoir protection; in addition, the increase in the amount of barite will increase the friction of the drilling fluid. A certain degree of increase, there is little research on the modification of this part

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