Experimental study of secondary crosslinking core-shell hyperbranched associative polymer gel and its profile control performance in low-temperature fractured conglomerate reservoir

摘要

Polymer gel as an effective plugging agent for profile control in depleted reservoirs has attracted extensive attention. Commonly, in-situ monomer gel, in-situ polymer gel and particle gel are used, while they can't satisfy the requirements of fractured conglomerate reservoirs. In this study, secondary crosslinking core-shell hyper-branched associative polymer gel formula was optimized according to gelation time and gel strength. The rheological properties and anti-shearing performance of first crosslinking gel, the effect of shearing on secondary crosslinking gel strength and the profile control performance of secondary crosslinking gel were studied under Xinjiang Oilfield conglomerate reservoir conditions. The results illustrated that first crosslinking gel exhibited pseudoplasticity property, which endowed its favorable injectivity. The hyperbranched structure, rigid core and hydrophobic pendants enhanced anti-shearing property of first crosslinking gel. The weak crosslinking structure of first crosslinking gel effectively reduced block solution filtrate loss and matrix damage, resulting in the effective entrance of first crosslinking gel into fracture and the formation of secondary crosslinking gel to control profile. All the results indicated that secondary crosslinking core-shell hyperbranched associative polymer gel has great utilization potential in low-temperature fractured conglomerate reservoirs.