Wang Yefei

Study and Application of Gelled Foam for In-Depth Water Shutoff in a Fractured Oil Reservoir

A gelled foam is comprised of water, a foaming agent (surfactant), a foaming stabilizer (polymer) and a cross-linking agent. This system with gel as the outer phase is more stable than conventional foam that uses water as the outer phase. Therefore, the gelled foam system prolongs the effective period of water shutoff. By using the Ross Foamer Device to determine its foaming and stability characters, we verify that the best foaming agent is 0.3% YG240; the stable foam agent is 0.2 - 0.4% HPAM; the cross-linking agent is 0.09% sodium dichromate and 0.16% sodium sulphite and nitrogen. On the basis of bench-scale evaluations of characters on gelation time and water shutoff efficiency, the pilot test is performed on Well H1340 in the Huoshaoshan fractured reservoir. The workover program includes washing the larger fissures using a highly efficient oil displacement agent, injecting gelled foaming agent, over-displacing fluids, nitrogen and water, then shutting in the well for hardening. Field tests show that good blocking efficiency is gained in the well with a water cut decrease of 20 - 50% and oil production increase of 3.7 - 11.0 m 3 /day.

The Application of Oily Sludge in Chinese Oilfield

Abstract Using industry wastes for conformance control has recently attracted significant interest—in particular, when using oily sludge for in-depth fluid diversion. About 500 tons of oily sludge is generated from oil production, transportation, and refining each year. Oily sludge is mainly composed of oil, water, o/w emulsions, and solids and is quite difficult to separate and reuse. The accumulation of oily sludge has posed a serious environmental problem. Additives such as suspension agents, dispersion agents, and viscosity thickeners are often added into oil sludge as conformance control agents to extend particle suspension time, increase plugging efficiency, disperse oily drop, and increase penetration depth. The advantages of oily sludge as conformance control agents include: (1) good compatibility with formation; (2) high temperature resistance; (3) high salinity resistance; (4) low costs; and (5) environmental protections. This method has been used by most oilfields in China, with better results.

Study on Components and Formulation of Liquid Gel Packer in Air Drilling

Abstract Air drilling is widely used in oilfields at home and abroad due to its ability to increase drilling speed significantly, reducing the drilling cost, protecting the formation effectively, and improving success rates in exploration. However, water breakthrough in formation is so serious that traditional methods of water shutoff cannot meet the demand of plugging while drilling, which restricts the application of air drilling. Based on the investigation and analysis at home and abroad, this article develops a new technique on blockage of water influx to the wellbore in air drilling. The technique involves the research and application of a kind of gel system used as a packer; that is, a liquid gel packer. The formulations of the gel packer, its effecting factors, and its loading capacity are studied at varied temperatures of 30°C–70°C. The study shows that the breakthrough pressure of the gel packer can reach 20 MPa, and materials such as sodium soil, scrap iron, and kaolin, which may exist in formations, can barely affect the gelation time and gel strength. All experimental results prove that the liquid gel packer has an excellent strength and wide suitability.