Abstract
Prevention of slightly cemented formation destruction and dispersed solids (sand and clay) removal is a complex and hitherto unsolved problem. The stability of the bottomhole zone is closely connected with geological and petrographic characteristics of the target formation and technological mode of producer wells operation. Sanding causes such complications like sanding-up, erosion of downhole and surface equipment, elimination of which requires significant financial costs. The adequate choice of bottom-hole zone stabilization, careful adherence to the elements of technological process are necessary conditions that guarantee technical and economic efficiency of works.
A variety of activities and methods are used in wells of "Azneft" PU to eliminate foregoing shortcomings, i.e. for sand control. Sand control activities mainly cover four areas: adaptation of gravel-slotted filter, drilling-in with no perforation, producing sand consolidation, sand plugs removal by means of tools.
Positive results have been obtained in the result of gravel-slotted filter application in 230 sanding wells. Drilling-in of weakly cemented formations with no perforation is carried out with or without the filter. Producing sand consolidation is realized using different technologies: control of physical and mechanical properties of the cement slurry, as well as cement slurries with various additives and polymer-based cement slurries.
Acid-based cement slurry is proposed to clean sand supplied from reservoir. Introduction of this technology creates a stable and permeable barrier in the near-wellbore zone that prevents or completely restricts sand entry.
In intake wells hydraulic, hydromechanical and wireline instrumentation is used to prevent the ingress of washing liquid for sand-bridge removal.
