Sulfate scale problems in oil fields water injection operations

Abstract

It is still a common practice to use available water for injection operations regardless of the water's contents of scale forming species, and then attempt to correct the problems that occur. Remediation of scale, particularly sulfate, tends to: (1) be very expensive; (2) be a trial-error procedure and field specific (e.g., almost no two identical sets of scale forming conditions exist in any two different fields, and thus any remedial solution cannot be generalized); (3) be successful only in less severe cases of scaling; and (4) cause more problems than they solve under certain conditions (e.g., formation of pseudo scales and extreme emulsion problems). In such a costly reactive approach, productivity decline due to sulfate scale is accepted as an economic compromise. Rather than extensively stimulating wells (backflow, hydralulic fracturing, acid wash, injection of dissolvers, etc.) with long-term remedial costs, and in some cases with irreversible damages (e.g., within the invisible oil-bearing formation), water injection operations should be designed properly from the start. If not, as typically the case, existing water injection operations must be corrected. This first article, in a four-part series, highlights sulfate scale problems in oil-fields water injection operations.