Acid fracturing has been part of Saudi Aramco's gas development strategy to maximize productivity from for vertical wells in the Khuff carbonates over the last several years. During acid fracturing, the wormholes created by the reaction with the formation results in excessive fluid loss. Controlling fluid loss is one of the key objectives in acid fracturing treatments to be able to create longer and wider fractures, and hence maximize well productivity. Alternating stages of polymer pad with diesel emulsified acid for deeper penetration and in-situ gelled acid, a polymer-based system, have been extensively used in most fracture treatements in an attempt to control excessive leak-off during the treatment.

The vertical well treatments target several reservoir sub-layers with varying degrees of porosity and permeability contrast. These layers are often divided by lithological streaks that make vertical communication challenging.Hence in many instances acid fracturing ends up over-stimulating the highest reservoir quality zones and by-passing or under-stimulating the other zones.Consequently, the zonal contribution from these wells is not optimal.

A pilot involving use of a new degradable fiber technology designed to achieve effective acid diversion during acid fracturing was recently implemented in several gas producers.The pilot comprised field trials in wells with similar reservoir characteristics and multiple porosity lobes.The treatments were designed and pumped with alternating stages of acid and fiber-laden polymer based pad fluid. The viscosity increase achieved in the pad by the addition of fibers and its bridging mechanism plugged off the just stimulated zones effectively, thus diverting the new stage of acid into the unstimulated porous zones. The fibers degrade and hydrolyze with temperature and time so no reservoir damage occurs.

This paper discusses the planning and design processes leading to the successful implementation of the technology, and the excellent post-stimulation results achieved. Bottomhole pressure gauge data were collected, and production logs were run to ascertain the effectiveness of the new technology.Results from the conducted pilot, along with production history comparisons with offset producers will be discussed.

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