Encouraging Results With a New Environmentally Acceptable, Oil-Soluble Chemical for Sand Consolidation: From Laboratory Experiments to Field Application

Abstract

The conceptual idea of chemical sand consolidation is to give the formation some additional residual strength in order to enhance the maximum sandfree rate (MSFR). Sand production in weakly consolidated reservoirs will occur when stresses in the well/perforation tunnel walls are large enough to disrupt the binding between the individual sand grains. This will generate a plasticised layer of sand in the near well bore area. The layer will erode by the produced fluid and may be transported to the surface. The rate of erosion will depend on the residual strength of the plastified material and the fluid rate. There is field evidence indicating a residual strength corresponding to the capillary force in water-wet sand to be sufficient in stopping or limiting the sand production substantially. Thus, only a small increase in residual strength of the plastified sand would make large contribution for enhancing the MSFR. This will have large economical implications in fields with wells controlled by MSFR. As the criteria for strength are quite low, search for potential treatment chemicals could be done in areas completely different from the traditional chemicals used in sand consolidation. Three different chemicals have been investigated and one has been brought further for laboratory qualification and field use. An important property is that the treatment system is oil-soluble. In contrast to water soluble systems, it will not alter the relative permeability in the oil bearing zones, thereby reducing the risk of increased skin due to changes in saturation. This oil-soluble system will be beneficial in fields with low reservoir pressure. The method is employed by simple bull-heading and will have a kind of self-diverting property. A team of engineers and scientists from different Statoil organizations were put on the job. New challenges regarding high water contamination, wells with difficult placements and zonal coverage, and a complex polymerization mechanism in the carrier fluid had to be solved. These experiences will be presented and discussed to gain valuable knowledge for future chemical sand consolidation operations. In this paper, the experimental data and field applications will be presented. In one well, oil production was doubled as a result of the treatment. Introduction Sand production from oil- and gas wells is a major problem in many parts of the world [1–3]. There are many problems associated with sand production, both regarding HSE (Health, Safety and Environment) and operational aspects. When sand is produced at a high velocity, it can cause erosion on any metal surface on its way. This is especially true for bends, valves and other points with a sudden change in flow direction. Erosion of process equipment can be a safety problem, but there is also an economical issue. Special care has to be taken when selecting materials at the points where erosion is a problem. The produced sand is usually captured in the first-stage separator and has to be jetted out. Furthermore, fine sandparticles might also influence on the separation efficiency of the process train topside. Why is sand produced? Many reservoirs are poorly consolidated, and both gas- and oil producing wells can experience sand production [4–6]. Changes in the stress conditions in the reservoir can lead to failure of the rock. A plastified zone is created and the fluid flowing in the well will erode this zone and bring the sand grains into the well. If the fluid velocity is high enough, the sand will be transported all the way to the surface. A rock failure is prerequisite for sand production, e.g. the fluid flow itself will not have enough energy to break loose the sand grains from the formation.

Experience With Chemical Sand Consolidation as a Remedial Sand-Control Option on the Heidrun Field

“…The field experience at Heidrun with the chemical has shown that correct placement is critical when it comes to performance with regards to increasing the MSFR. This is in accordance with previous field experience with the sand consolidation chemical 6 . Although difficult to deduce, reduction in PI does not seem to be a major concern in these treatments.…”

Application of Concentric Coiled-Tubing and Well-Vacuuming Tool With Chemical Sand-Consolidation Resins for Controlling Sand Production in Wells With Damaged Screens or Slotted Liners: A Rigless Well-Repair Alternative

“…Its use also leads to increased consolidated system resistance to chemical attack and degradation (Harrisberger et al 1971). In particular, organosilanes coupling agents family have been applied alone (Kotlar et al 2005, Kotlar et al 2006) and mixed with resins (Walther et al 1966;Spain 1967;Nguyen 2007).…”

Field Experience With Chemical Sand Consolidation as a Remedial Sand Control Option

“…The chemistry and details regarding the chemical can be found in other publications [9,12]. The stabilized sand matrix can therefore withstand higher hydrodynamic forces from the fluid flow and thereby prevent the erosion and transport of sand grains into the wellbore and possibly all the way to the process facilities top-side.…”

“…These are described elsewhere [9,12] Case histories. Strength of 50 bar differential pressure can be obtained with low concentrations of organosilane.…”