Abstract
The success of all oilfield chemical treatments is dependent upon fluid placement efficiency. In acid-stimulation treatments, the acid should be placed so that all potentially productive intervals accept a sufficient portion of the total acid volume. The same is true for scale-inhibitor squeeze treatments. It is critical for the inhibitor to be distributed as uniformly as possible over the interval of interest.
Various diversion techniques are available to assist in alteration of the injection profile during matrix treatments. Likewise, several computer design programs are available to advise on appropriate diversion techniques and allow numerical simulation of the diversion process and efficiency. Rarely are placement models validated in the field.
Recently, a joint project was initiated to develop a novel fluid-diversion process. This project resulted in a particulate-diversion agent that has several advantages over traditional particulate diverters. Advantages include little or no environmental impact, negligible solubility at surface conditions, controlled permeability of the filter cake or perforation pack, upper temperature limit significantly higher than traditional diverting agents (excluding salt), compatibility with nearly all treatment fluids, diverter degradation at bottomhole conditions to eliminate post-treatment removal, and excellent regained permeability.
The chemical development is not the only unique and novel aspect of this joint development. An extensive field trial was conducted, incorporating multiple step-rate tests, fluid-efficiency tests, treatment-pressure matching, pressure-buildup tests, temperature surveys, and injection profiles. These tests were performed in a 226°F sandstone reservoir at approximately 11,900 ft MD. Testing was performed (1) before diversion, (2) during injection of the diverter, (3) immediately after diverter placement, and (4) finally 1-2 days later to confirm diverter degradation. The pressure-matching techniques used in this study would not be unique in proppantfracturing applications; however, the application to matrix stimulation and chemical placement techniques using both pressure matches and injection profile matches are unique and novel processes.
