Abstract
Summary
Historically, emulsified acids have primarily been used in fracture acidizing. By combining information from theoretical studies, experimental studies, and field testing, a better understanding has recently been gained of the application of emulsified acids in matrix acidizing. This paper discusses the use of emulsified acid as a stimulation fluid for matrix treatments in heterogeneous carbonate formations.
Emulsified acid is diffusion retarded which makes it an effective wormholing fluid at low injection rates that occur, for example, in low permeabiliy or damaged formations. At these low rates, plain HCl acid will mostly spend on the formation face and is unable to create wormholes that penetrate deep into the formation.
In this paper, results of flow tests are presented that compare the efficiency of emulsified acid with that of plain HCl acid. Several emulsified acid systems were tested. The effects of the injection rate, viscosity, and acid/oil volume ratio were analyzed on core samples. Rheological properties and temperature stability (up to 250°F) of the emulsion systems were analyzed by means of Fann-50 tests.
Acid-in-oil emulsions are effective stimulation fluids in large intervals where streaks of high permeability can act as thief zones. This is shown by means of example calculations of the fluid flow and distribution in a well.
Publisher
Society of Petroleum Engineers (SPE)
Cited by
24 articles.
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