Squeeze Cementing in Carbonate Reservoirs

Production in the West Texas area is primarily from carbonate (dolomite and limestone) reservoirs. This environment presents a special set of conditions in the realm of squeeze cementing. Techniques have been modified in recognition of these features. As a result, a formerly poor squeeze record in the area has seen noticeable improvement. A major problem in this carbonate background is the existence of fracture network systems. These fractures occur naturally, are created inadvertently during drilling and completion, or result from well stimulation efforts. To compound the difficulties in remedial squeeze efforts, they are of probable vertical extension. This is supported by modern theories on hydraulic fracturing, and temperature and radioactive tracer work. Other common problems include abnormally low temperature gradients, low standing well fluid levels, and long intervals of perforations. In contrast to squeeze cement applications in permeable sandstones where prime interest is basically on slurry behavior within the perforations (or at least of nominal penetration), a major consideration in squeezing in a carbonate environment is the cement fill of fractures and/ or channels. There is less emphasis on filter cake buildup. This approach results in the use of larger volumes of slurries than normally used in squeezing of permeable sandstone reservoirs.