Gravel packing, being one of the most reliable and robust downhole sand control techniques, is often the preferred method for establishing sand control. In reservoirs where the pressure has fallen below the water gradient, gravel placement using water based fluid will produce a high overbalance leading to excessive losses of fluid that might deeply invade the formation, cause premature bridging, and fracture the formation. The main focus of this paper is to identify fluids and techniques for gravel packing a depleted reservoir and evaluate the best technique and a fluids package for a candidate well.
A well candidate in the Mediterranean is planned to be completed with cased hole gravel pack and it is a twin of a cased and perforated gas well that started producing formation sand after 4 years of production. Continued production from the reservoir is expected to drive down the pressure to 7.5ppg by the time, when candidate well is completed.
Several techniques for gravel packing a depleted reservoir have been considered which included diesel, alcohol-, oil-, gas- and water-based fluids. However after extensive lab testing the most suitable fluids package for the well was found to be conventional water packing. Contrary to expectation, formation damage tests indicated that water based gravel packing caused less damage than non-viscous oil based fluids for this particular candidate well. Solids-free high-temperature perforation kill pill and breaker package were also designed for the well to be stable for up to 4 days, which pushed the limits of solids free kill pills currently available in the industry.
The paper will discuss in detail the gravel packing fluid package selection methodology, and completion fluid, gravel pack fluid, kill pill and breaker fluids package design and evaluation for the candidate well.