Why consolidate sand?

Many of the world’s oil and gas wells produce from poorly consolidated sandstones. The sand grains freed from these rocks as oil is produced causes problems such as plugging of perforation tunnels, sanding up of production intervals, accumulation in surface separators and potential failure of downhole and surface equipment. This poses serious economic as well as health and safety risks.

Principal aims of project

1. to bind sand grains together with a polymer coating thus maintaining the strength and permeability of the sand formation
2. to target the treatment by controlling the position and extent of consolidation relative to the wellbore

Treatment strategy

The objective is to bind sand grains together whilst maintaining formation porosity and fluid flow. This is achieved by producing a coating on the surface of the sand grains by careful control of the composition of the specially formulated treatment fluids. A strong coating which does not adversely affect permeability is produced by forming a surfactant bilayer (admicelle) on the sand surface. This creates a favourable environment for polymerisation.

Advantages over conventional treatments

In comparison to resin and furan based technologies, the current treatment has several practical and economic advantages

• fewer injection stages: two stages as opposed to the 4-5 required with conventional treatments
• retains most of original permeability (furan and resin based treatments can reduce porosity by blocking the pores between the sand grains)
• works at typical downhole temperatures of the North Sea (70 oC) in a saline environment
• experimental cores meet unconfined compressive strength and permeability targets

ESEM (Environmental Scanning Electron Microscope) studies of consolidated sand

ESEM operates at low vacuum and does not require a conductive coating, therefore samples were little altered from when they were extracted from the sandpack. This has proved invaluable in determining the morphology and coverage of the polymer coatings.