Research and Field Application of Polymer-Multiple Emulsion Crosslinker Gel for the Deep Profile Control

Abstract

The authors describe a means to prolong gel time of Cr(Ac)₃-polyacrylamide gel system by coating the Cr(Ac)₃, forming the W₁/O/W₂ crosslinker. The white oil is the oil phase, and the sorbitol fatty acid esters are the water-in-oil emulsifier. The polyoxyethylene sorbitan monostearate is the oil-in-water emulsifier, which has a national patent (cf. Wang et al., 2009). The authors researched the effect of the reactants concentrations and reservoir environments are investigated to gelling behavior and plugging capacity such as temperature, salinity, and permeability. Compared to the Cr(Ac)₃ without coating, the multiple emulsion crosslinker obviously delays crosslinking and greatly increases gel time by about 3–4 times, so it is conducible to deep profile control. Reactant concentrations and temperature increase the gel strength and plugging capacity, but shorten gel time. Salinity causes gel time to shorten and lengthen, and gel strength weakens before it increases. Permeability reduces the plugging capacity and presents in linear relation in the log-log coordinate. Four wells were tested successfully in Shengli Oilfield from May to November 2008. The average injection pressure-added is 2.5 MPa, and approximately 3,200 tons of incremental oil was obtained with 6% water-cut decrease.

Keywords:

• gelation behavior
• deep profile control
• delay crosslinking
• multiple emulsion crosslinker
• sealing ability
• W₁/O/W₂