A new polymer system, referred to simply as the AP-P4 polymer system, aims at solving the problems of high temperature, high salinity and the poor shearing resistance, all of which are encountered by conventional polymers (such as polyacrylamide) used in profile control, profile performance improvement and EOR operations in the Zhongyuan Oilfield, Sinopec. This system has been developed on the basis of the specific molecular structure and the better properties of high temperature resistance, high salinity resistance and strong shearing resistance of the new type of AP-P4 association polymer. Acidity modifying agents and cross-linking agents (MZ-YL, MZ-BE, MZ-XS), compatible with the new polymer system, are selected. Results of performance tests have shown that the new polymer system has excellent thickening, high temperature, high salinity and shearing resistance and anti-dehydrating properties. In 2003, it underwent its first pilot test in 26 wells in China, with remarkable effects in increasing oil production and decreasing water production. The newly developed polymer system and its application technology described in this paper may play a guiding role in polymer profile control operations in the oil reservoirs of high temperature and high salinity.
Plugging agent treatment and acid stimulation have completely different mechanisms for improving injection profiles. In this paper, a hybrid procedure is introduced to reduce the damage of the plugging agent to low and medium permeability zones and the penetration radius of acid into high permeability zones. The procedure is: First inject plugging agent to block high permeability zones, and then inject acid to remove plugging agent damage from the low and medium permeability zones and stimulate them. To perform this procedure successfully, three kinds of plugging agents, namely strong strength plugging agent for the wells with fractures or high permeability streaks, weak gel for those with thick layer in which serious heterogeneity exists, temporary plugging agent for those in which the absorption ability of high permeability zones needs maintaining, were screened out for use in different reservoirs. Several acid systems were evaluated to be compatible with the three kinds of plugging agents. The objectives of this paper are:(1)To show the screen results about the compatible plugging agent and acid; 2 To show how to optimize the operation process;(3)To tell some experience gained ( ) from the oilfield applications of this technique. From Jan. 2001 to Dec. 2002, 46 operations using this procedure were carried out in Weicheng and Mazhai Oilfields of SINOPEC. Results show that the average benefit/cost ratio is over 3.5. Experience acquired from these applications was summarized in the paper.
