Scope of Application:

This technology is applicable to water well in oil reservoir with high water content for deep zone displacement and profile control by easing interlayer and in-layer contradictions.

Principles

To block the different cross-flow channels in deep zone by complex plugging, it can be achieved by injecting organic or inorganic gel plugging agent, forming accumulation membrane through underground flocculation reaction to block fissure and big pore, then plugging high permeable belt and big pore with expandable gel system, additionally injecting late crosslinking gel system to expand displacement control radius and further increase the fullness of stratum resulting in changing direction of injecting water and improving efficiency of water driving.

Meanwhile, this gel system can move to deep stratum by the driving force of injecting water and fill smaller pore and fissure. Seal plugging of strong gel system will be ultimately applied, it can protect main plugging and prevent round flow of injecting water to extend the validity of operation. The integrated process of profile control, plugging and displacement is accomplished by combination plugging to achieve the goal of adjusting water-absorbing profile and increasing recovery efficiency.

Configuration of Complex Displacement Control System in Deep Zone 

Four functional pluggings are designed for complex displacement control in deep zone, as their functions as follows: 

Plugging I: to inject organic gel or inorganic gel in turn, perform reaction underground, block fissure and big pore;

Plugging II: expandable gel system, to block high permeable belt and big pore;

Plugging III: to delay crosslinking system, change fluid direction in deep zone and activate  oil remainder;

Plugging IV: strong gel seal plugging, to protect main plugging, prevent round flow of injecting water and extend validity.

Technical Indicators and Performance Features

1.Pumpability: underground crosslinking, ground fluid 

2.Low critical concentration of gel formation: 0.15% polymer, 0.02% concentration of crosslinking agent for performing crosslinking

3.Period of gel formation controlled: 2 – 6 days adjustable

4.Strong anti-shear ability: viscosity deduction of formed gel at 60°C is less than 10% after sheared.

5.High strength after gel formation: the formed gel is of viscosity and elasticity; viscosity is more than 20000mPa·s.

6、  Heat resistance, salt tolerance and stability: in water with mineralization degree of 15×104mg/L, viscosity at 90°C no less than 20000 mPa.s.

Field Applications

Since 2005, this technology has been applied to 410 wells with 100% success ratio at Zhongyuan,Yanchang and Changqing oil fields. The average pressure of injecting water rises by 3.8 MPa after operation, daily oil production of well group up by 2.05t, water content of well group down by 16.3% of mean value. The condition of water-absorbing profile has been improved to help accomplish deduction of water and increase of oil production.