Application of Solid Scale Inhibitor in Annular Space to Reduce Well Intervention Cost

Abstract

Abstract Formation damage caused by mineral scale development is one of the major reasons resulting in reduction of hydrocarbon production during a well's life cycle. Scale inhibitors are most widely used to control scale deposition in producing wells either by adding them directly to fracturing fluids in wells where stimulation treatment is planned or by performing remedial squeeze treatments. Prolonged protection can be achieved by adding proppant-sized solid inhibitor during the stimulation treatment. The current study addresses the benefits of alternate methods of placing solid inhibitor depending on the well completion system. In the case where stimulation treatment is not planned, the solid inhibitor can be placed in the annular space between the production tubing and formation in the long open-hole horizontal well to provide extended protection as the well starts to produce. This solid inhibitor once depleted as evidenced by residual analysis can be recharged effectively by injecting liquid inhibitors that restores the effectiveness, allowing extension of protection life-times. An appropriate inhibitor chemical was first identified for the treatment from the produced water scaling analysis. A suitable solid scale inhibitor was prepared by adsorbing this chemical onto a high surface area water/oil insoluble substrate, and multiple surface modifications made to control the inhibitor release rate. The long term inhibitor chemical release profile was evaluated by packing this solid inhibitor into a column and eluting with synthetic produced water at expected bottom-hole temperatures of 200°F. The solid inhibitor elution tests show long protection times when solid inhibitor was applied. The projected inhibitor protection would be more than 60,000 pore volumes (PVs) of produced water before the inhibitor chemical was substantially depleted. In a well, 3000 pounds of this inhibitor can be potentially placed in the annular space, which would result in preventing scaling for 330 thousand barrels of water being produced, with protection life-time of more than 5 years (at 170 barrels of water per day). The presence of high surface area substrate allows inhibitor to be recharged after inhibitor depletion. The efficiency of the inhibitor recharge application was investigated by a series of column experiments. Placing the solid inhibitor into the annular space will delay the requirement for scale squeeze treatments significantly, and reduce the overall well maintenance cost for the operator, particularly in an offshore environment. The ability of the solid inhibitor to be re-charged using conventional scale squeeze chemistry enables more chemicals to be retained when subsequent squeeze is potentially performed on the wells.