In-situ sand consolidation by low-temperature oxidation

Low-temperature oxidation (LTO) of crude oil has been investigated, for its potential as a sand consolidation technique. Loose sand (20/30 mesh) saturated with crude oil (18 to 20 degrees API) and brine was subjected to air injection at a low temperature (100 to 150 degrees C) for a period of time (6 to 18 hours). The sandpacks developed compressive strengths ranging between 375 and 1,264 psi. The permeability loss due to consolidation was between 4.5 and 22%. It was found that higher oxidation temperatures reduced the consolidation time and increased the compressive strength; but had no effect on the magnitude of permeability loss. Heavier oils required less oxidation time, caused slightly larger permeability losses, but had an insignificant effect on compressive strength. The presence of clay enhanced the LTO reactions by shortening the oxidation time and increasing the amount of residue deposited on the sand grains. This greatly increased the compressive strength, but at the expense of larger permeability losses. When interstitial water was present with clay, the permeability loss was increased further while the compressive strength was slightly reduced. Acid treatment had no effect on the residue deposited on the sand grains. Experimental testing as well as two predictive models showed that this technique provides sufficient compressive strength to withstand sand-free, high-flow velocities and results in much smaller permeability losses compared with plastic consolidation. It is planned to test the consolidation process in one of the fields in the Middle East. Work is in progress to optimize the process parameters for the conditions of this held to be able to test the process on the first well by December 2000.