Operator needed to improve stimulation of high-temperature dolomite reservoirs

The most important reservoirs in the southern region of Mexico are from deep, high-temperature, naturally fractured dolomitic-limestone formations. These reservoirs must be stimulated to achieve—and sustain—economic production rates. However, high temperatures and mixed mineralogy present a number of issues, including acid placement, tubular corrosion, water breakthrough, and increased risk of fluid incompatibility resulting in formation damage. With temperatures exceeding 300 degF [149 degC], there is also a tendency for acids to spend on the face of the formation at the wellbore or become lost in nonproductive thief zones.

Schlumberger introduced chelant-base stimulation fluid

Less than one year after being completed, water breakthrough forced the operator to recomplete the well and to stimulate the well by bullheading a combination of organic and inorganic acids. After the treatment, production increased from 700 bbl/d up to 1,388 bbl/d with a 0.5% water cut. However, after reevaluating well performance, the operator discovered the well had a positive skin.

To optimize the stimulation efficiency to remove drilling fluid and near-wellbore damage, Schlumberger proposed a combination of CLEAN SWEEP solvent systems for damage removal and chelant-base NARS treating fluid, as a more effective alternative to conventional acid systems in high-temperature dolomite formations.

NARS fluid removed skin damage, increased oil production 33%

The NARS fluid successfully removed any remaining formation damage, reducing the formation skin from 2.2 to 0. As a result, oil production which was 1,388 bbl/d after the previous conventional stimulation treatment increased to 1,840 bbl/d. In addition, well cleanup time decreased by 3 days, helping the operator to save 3 days of deferred production—the equivalent of saving USD 500,000.