Enzo Pitoni

Rigless WSO Treatments in Gas Fields. Bullheading Gels and Polymers in Shaly Sand: Italian Case Histories

Gels are used worldwide to control water co-production in gas and oil wells (WSO treatments) but the criticality of a correct placement in the Italian scenario had strongly limited their use in this Country. For instance, in gravel packed wells or in wells where the ID casing/ID tubing ratio is over 2.5, inflatable packers cannot be efficiently used for gel diversion; moreover, dual injection has to he usually applied with these tools, making a treatment very often too expensive and, as a result, unacceptable. A review of water problems and displacement data collected during past matrix treatments performed in Italian gas fields led to the study of possible alternatives for treatments to he performed using standard crosslinked polymer and unusual displacement techniques. Relative Permeability Modifier (RPM) polymers were also considered and lab tested for WSO in shaly sands because the use of gels is still considered too risky. In fact, most of the treatments performed in Italy have to he performed bullheading in order to reduce the cost of the operations, making WSO treatments more attractive. In this paper a brief summary of laboratory activities for a correct selection of polymers and gels, suitable for shaly, low permeability sands are reported as well as field treatments data and results. Bullheading technique seems to he the only cost-effective and field proven placement method for rigless WSO treatments to produce marginal gas reserves from shaly, depleted, low temperature, multilayered reservoirs.

Dual openhole gravel pack in shaly fine sands

This paper discusses the design and execution of dual-zone gravel packs in very shaly and silty formations of median sand grain size less than 30 {micro}m. An oversized gravel was selected for sand control and, as a consequence, the openhole gravel-pack technique was adopted to reduce the effect of intermixing between formation and gravel-pack sand. During the completions in the first five wells, the authors encountered and solved several operational problems, including those involving (1) borehole stability, (2) setting of inflatable packer for zone isolation, (3) hole preparation, and (4) gravel placement. From the lessons they learned, another 11 wells were completed with dual openhole gravel packs without significant problems. After 1 year of production, the flow performance from the wells met or exceeded the initial objectives.