Dirty Sand Consolidation Technology for Gas Wells

Abstract

AbstractItalian gas fields are usually composed of many sand layers, which must be produced separately: therefore, multiple completions are very common in Italy. Shallower layers, the most prone to produce sand, are completed with sand control techniques: open hole gravel pack and inside casing gravel pack installed above fracturing pressure (frac pack)1–3 are the most popular completions. Sometimes shallower layers can not be completed in sand control just because the uppermost selective gravel pack on short string was installed in a deeper, more prolific, sand layers. Conventional completion (without sand control) is the only possible technique applicable in these layers.Formation sand can not be consolidated with standard chemical treatments (e.g. resins) because of the high clay content (25–50%) and the low permeability (10–200 mD). The use of frac pack with resin coated proppant is not allowed by the thin thickness of sand layers where the fracture can extend toward close water layers. A novel sand consolidation technique especially suited for prevention of dirty sand influx in gas wells has been developed. Laboratory testing of the new sand-control system gives a minimum 70–80% permeability retention and the resulting compressive strength is sufficient for an effective sand control. The cementing materials, as shown by SEM (Scanning Electron Microscopy), can be described in terms of precipitation of amorphous silica and migration of clays.This paper reports the laboratory testing and results: the novel system is able to consolidate very low dirty permeable sands (< 1 mD) containing high concentration of clays (up to 50%) and carbonate materials (up to 20%)This technology has been employed in field trials with positive results.