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A well flushing fluid for low water cut oil wells

A technology of well flushing fluid and low water content, applied in drilling compositions, chemical instruments and methods, etc., can solve the problems of low diesel viscosity, high intrusion amount, and difficulty in preventing the infiltration of water into the oil layer, etc., and achieves high mutual solubility, The effect of reducing pollution

Inactive Publication Date: 2018-08-17
CHINA UNIV OF PETROLEUM (EAST CHINA)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The flushing fluid used in the early stage is mainly to add temporary plugging agent to the water phase system to reduce the intrusion of water phase, but it is difficult to prevent the infiltration of water phase into the oil layer, and the temporary plugging agent is also easy to pollute the oil layer
The traditional oil-based drilling fluid mainly adopts diesel oil system, although it can reduce the impact on the oil phase permeability, but the cost of diesel oil is high, and the low viscosity of diesel oil still has a high intrusion, which increases the cost of well cleaning operations

Method used

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  • A well flushing fluid for low water cut oil wells

Examples

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Comparison scheme
Effect test

Embodiment 1

[0015] Disperse nano-silica with an original particle size of 15-30nm into biodiesel to form three systems with a mass fraction of nano-silica of 1%, 3% and 5%, respectively. The viscosity at the speed is shown in Table 1. It can be seen that when the shear rate ≤ 0.01S -1 , the viscosity of the system is greater than 6×10 4 mPa·s, when the shear rate ≥ 80S -1 , the viscosity can be reduced to 120-330mPa·s.

[0016] Table 1 Viscosity of nano-silica thickened biodiesel at different shear rates

[0017]

Embodiment 2

[0019] Disperse nano-silica with an original particle size of 15-30nm into biodiesel to form three systems with a mass fraction of nano-silica of 1%, 3% and 5%, respectively, and measure the concentration of nano-silica in the three systems. particle size distribution. The results show that nano-silica has a wide particle size distribution in biodiesel, and the particle size ranges from 100nm to 30μm, so it can temporarily plug the percolation surface of the oil layer.

Embodiment 3

[0021] Disperse nano-silica with an original particle size of 15-30nm into biodiesel to form three systems with a mass fraction of nano-silica of 1%, 3% and 5%, respectively, and measure the three systems at different permeability The results of the fluid loss rate in the core are shown in Table 2. It can be seen from the table that when the permeability increases, the fluid loss rate begins to decrease, but the overall fluid loss rate exceeds 90%.

[0022] Table 2 Fluid loss control performance of well flushing fluid

[0023] Core permeability / (×10 -3 μm 2 )

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Abstract

The invention provides a well flushing fluid for oil wells with low water content, which is prepared from nano-silicon dioxide and biodiesel, wherein the nano-silica accounts for 1%-5% of the total weight. The well flushing fluid has good shear dilution and high filtration loss reduction ability, which can fully clean the oil casing and maintain the oil phase permeability in the oil layer. The well-flushing fluid system has a filtration rate reduction rate of more than 90% and an oil-phase permeability recovery rate of more than 98%.

Description

Technical field: [0001] The invention relates to a well flushing fluid, which is used for reservoir protection of oil wells with low water content. Background technique: [0002] During the development of oilfields, due to operations such as pump replacement and pump inspection, it is necessary to use well-entry fluid to circulate and clean the casing annulus and tubing. At present, the water phase with surfactants is mainly used as the well-flushing fluid, but for the water content In lower oil wells, after the water phase in the well fluid invades the oil layer, it will emulsify with the crude oil in the oil layer, thereby increasing the resistance of crude oil flow, and changing the flow form of crude oil in the oil layer from single-phase flow to two-phase flow. The relative permeability of the oil phase is greatly reduced. The invasion of well flushing fluid will greatly reduce the production of oil wells after production is resumed. Therefore, for low water cut oil we...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C09K8/52C09K8/502
CPCC09K8/502C09K8/52C09K2208/10
Inventor 蒋平张磊葛际江张贵才裴海华王洋
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)