This paper describes the performance evaluation of curable resin coated proppants currently used in Russian Oilfields. The performance of these RCPs is compared based on established API/ISO standards and standard resin coated proppant testing methods currently applied within Schlumberger. These methods investigate further fluid compatibility between fluid systems and resin, proppant pack integrity under a variety and combination of curing conditions and proppant pack integrity under well flowing conditions. In the paper we evaluate the material performance of resin coated proppants used in Russia, showcase new resin coated proppant testing methods and demonstrate the need for firm industry standards devoted to the testing of resin coated proppants.
Introduction
A common problem after the fracturing stimulation of a well can be the back production of proppant[i],[ii] (proppant flowback). Proppant flowback can occur instantly during well cleanup, over a period of several days to weeks after the fracturing treatment and during the economic life of the well. Proppant flowback often leads to poor fracture conductivity in the near the wellbore region due a reduction in fracture width. This width reduction can act as a choke limiting production from the entire fracture. Proppant that flows back can have a detrimental effect on production equipment, lead to plugging or erosion of surface and downhole completions and lead to loss of revenue during down time when equipment is replaced. In some cases up to 15 % of the proppant placed during a fracture treatment has been known to return during the clean-up period. Root cause analysis of ESP failures attribute up to 30% of the failures to solids/proppant production. The net impact of proppant flowback can result in reduced production, damaged equipment and ultimately loss of revenue. Some method of flowback control is usually implemented to avoid issues with proppant flowback and maximize fracture production.
Existing solutions for proppant flowback include curable resin coated proppant (RCP), fibers, deformable beads and resin on-the-fly. The most popular of these solutions remains curable resin coated proppant. Since the late 1970s, curable RCP has been used to control proppant flowback[iii]. The curable resin coatings are designed for a variety of downhole temperatures and can be applied to a variety of sand and ceramic substrates depending on the crush resistance and conductivity required. The effectiveness of using RCP as a proppant flowback control tool has been confirmed by multiple laboratory studies, ?s well as long-term experience of its application. It is widely accepted[iv] that the long-term flowback control, sand control and conductivity resulting from curable RCP is due to the following reasons:chemical consolidation between proppant grains resulting in high compressive strength;higher crush resistance than the substrate due to more effective distribution of stress between particles; andresin coating keeps fines encapsulated after failure of the substrate.