Accelerated low-temperature oxidation for sand consolidation and production control

Abstract

Sand production that occurs in poorly consolidated oil and gas reservoirs causes many serious operational problems. Industry experts have used both chemical and mechanical sand control techniques to overcome this challenge; however, these techniques have various technical and economic limitations. For example, a technique that employed in-situ low-temperature oxidation (LTO) of an asphaltic solution saturating the near-wellbore area helped increase the formation's compressive strength while retaining its permeability; however, this technique was time-consuming at low reservoir temperatures. This study employed thermochemicals to preheat the sand and thereby accelerate the LTO reaction and shorten the consolidation process. First, small packs of loose sand saturated with an asphaltic solution were oxidized via external heating until consolidation. The optimal conditions involved continuous airflow for 6 h at 180 °C, which produced consolidated sand with a compressive strength exceeding 12.4 MPa. Second, a similar but insulated saturated sand pack was flooded with several pore volumes of thermochemicals, which raised its temperature from 75 °C to 188 °C; this was followed by 6 h of air injection. The consolidated sand had a compressive strength of 10.27 MPa and showed excellent stability against acid and crude oil floods as well as prolonged soaking in toluene.This study demonstrated the potential of using thermochemicals for the in situ heating of the wellbore area to elevated temperatures for sand consolidation. By shortening the treatment time, the thermochemicals improved the cost-effectiveness of sand consolidation via LTO without adversely affecting the consolidation quality.