ONGC is in the core business of exploration and production of oil and gas from various Onshore and Offshore fields in India. Oil and gas is usually trapped in porous rock composed of sandstone or Limestone. Many of the sandstone formations are poorly consolidated which leads to the production or incursion of sand and fines particles along with oil or gas.
Sand production can drastically effect on production performance of the wells, damages downhole equipment and surface facilities and increases the cost of production. It can also causes wellbore stability problem, casing collapse, reduced production and in extreme cases, loss of wellbore.
Unconsolidated or poorly cemented grains are mobilized at certain pressure drawdown levels with fluid velocities and viscosities. Sand grains produced in fast flowing conditions erode tubular and can become stationary or migrating obstruction. The erosive capability of produced sand depends on many factors including the amount of sand, sand particle velocity and impact angle. In subsurface, the main factors that control whether a reservoir will fail mechanically are rock strength, the effective stress on the formation- which is the principal earth stress acting on the rock minus the pore pressure and the stress induced by drilling, completion and production.
Unconsolidated sandstone reservoirs with high permeability are most susceptible to sand production, which may start during first flow or later when reservoir pressure drops or water breaks through. Usually, mechanical sand control methods like sand screen, gravel packing etc. and chemical sand consolidation are being used to address the problem.
To increase the production and better recovery of hydrocarbons, many of the oil and gas wells are drilled and completed in pay zone horizontally. The sand control in horizontal wells is even more challenging.
II. Boundary Conditions
• The sand control measure should stop the sand production without any effect on oil and gas production.
• Should be applicable in vertical, deviated as well as in horizontal wells in Onshore and Offshore fields.
• If chemical sand consolidation method is used, it should not have any detrimental effect on the producing formation and on productivity of the well.
• The method/technique should be applicable to the well/reservoir up to 4000 m.
• The method/technique should be applicable to the reservoir temperature range of 600C to 2000 C and reservoir pressure up to 10,000 psi.