Acidizing Dolomite Reservoirs Using HCL Acid Prepared with Seawater: Problems and Solutions
MetadataShow full item record
Seawater is the only viable water source for many offshore wells with dolomite formations. For these wells it is important to use compatible fluids when stimulating to avoid damaging the formation with calcium sulfate precipitation. Much work has been conducted on this problem for limestone, but there have been no publications about calcium sulfate precipitation within dolomite during matrix acidizing. This work quantifies permeability damage when acidizing using hydrochloric acid mixed with seawater and no scale inhibitors. Scale inhibitors were also tested for effectiveness in reducing calcium sulfate scale during acidizing. Static jar tests of three phosphonate-based, two sulphonated polymer-based, and one polyacrylic-based scale inhibitors in spent acid systems were used to compare the effectiveness at temperatures ranging from 77 to 325°F. Corefloods were conducted to investigate the extent of calcium sulfate precipitation without scale inhibitors and to test permeability improvements with the addition of compatible scale inhibitors at temperatures up to 325°F. This work shows that calcium sulfate precipitation within dolomite during matrix acidizing with seawater and hydrochloric acid will damage the well. Corefloods with seawater showed a permeability reduction of 30% or greater compared to corefloods with freshwater for all temperatures tested when no scale inhibitors were included in the acid solution. Calcium sulfate precipitation was determined to be the cause of the decreased permeability. DTPMP, a phosphonate-based scale inhibitor, and a sulfonated polymer scale inhibitor at concentrations of 150 ppm were shown to effectively reduce calcium sulfate scale with minimal inhibitor/rock reaction during these tests. The ability to improve stimulation effectiveness by the addition of compatible scale inhibitors to the acid solution is critical information to prevent damaging dolomite formations during matrix acidizing with hydrochloric acid and seawater.
Arensman, Dennis G (2014). Acidizing Dolomite Reservoirs Using HCL Acid Prepared with Seawater: Problems and Solutions. Master's thesis, Texas A & M University. Available electronically from