Some Factors Influencing the Plugging Characteristics of an Oil-well Injection Water

A test for determining the plugging characteristic of an oil-well injectionwater has been developed. It consists in measuring changes of the filter rateof a water at constant pressure with cumulative throughput when passing thewater through a medium grade sintered glass disk. Application of the testmethod was made to the water used in the Union Oil Company's experimental waterflood of the Chapman zone in the Richfield field, Orange County, California.This water developed increasing plugging tendencies upon aging, even though thefinished water from the plant filter exhibited few such characteristics. Theplugging material was found to consist of calcium carbonate, ferric hydroxide, and organic substances that were presumed to be bacterial. Various method of stabilizing this water to prevent the formation of pluggingmaterial were attempted. Lowering the pH to approximately 6.4 by injectingcarbon dioxide provided a moderately satisfactory means for stabilization but abetter method of stabilizing this water was found to be first aging and thenfiltering. Introduction An experimental water-flood project was started oil the Chapman zone of theRichfield field in March 1944 and has been described in a previous paper. Itconsists of a single injection well drilled between old producing wells. Awater-treating plant using primary alum flocculation, sedimentation andchlorination followed by secondary flocculation, sedimentation and filtrationis employed to process the water before injection. In all of the water-treatingoperations, the system is open to the air, and no attempt is made to preventthe loss of carbon dioxide or absorption of oxygen by the water. The clearwater is stored in a covered concrete basin and pumped through a Transite lineto the suction of a high-pressure pump at the injection well. The high-pressuretubing in the well to the injection zone is cement lined. The untreatedinjection water is a mixture produced with the oil from the Chapman and Kraemerzones and is supplied from the disposal system. Because the injection well was relatively deep (injection zone about 3400'Ft.)and would be expensive to replace, it was believed imperative to supply anonplugging injection water and to develop laboratory procedures for evaluatingthe treated injection water with respect to its formation plugging properties.This report describes the development and application of the test procedurebased on the assumption that the plugging properties could be determined bymeasuring the progressive decrease in flow rate of the water through a porousmedium. If the quality of the injection water was good enough so that theplugging action on the Porous medium was of small magnitude, it was reasonedthat the tendency to impair flow in the formation would not be serious. T.P. 2028