Scaling precipitation in the form of calcium or iron sulfate (CaSO4 – FeSO4) appears to be a common problem in most of the wells completed in the Yeso formation in the Permian Basin. Accumulation of these forms of scale in the perforations and the downhole equipment can create severe production losses and therefore they require constant, some times costly, treatments. Additionally, their presence in the wellbore hinders the efficiency of the acidizing procedures, performed by the operators to further increase the productivity of their wells.
The objective of this paper is to present an innovative workflow, which significantly reduces the scaling effects and allows the acidizing of these carbonate reservoirs to be more efficient. Results are avialble for more than 20 wells, from Occidental Petroleum’s assets in the North New Mexico region. Details regarding the evolution of the procedure, the types and amounts of the chemicals are extensively discussed in this paper.
The procedure starts with the candidate well selection, which preferably are located in the highest OOIP areas to maximize the efficiency. The second step involves the water sampling and analysis to determine the types of scaling and consequently the required chemical treatment. The innovation in this step has to do with the time that converters are left in the wellbore and the extra chemicals that have been added compared to the previous procedures. The last step involves the deployment of the acid downhole, where three different methodologies have been tested and evaluated based on their efficiency and well returns.
The proposed approach has been successfully applied to more than 20 wells and the results are encouraging showing an average incremental oil production of ~600% while the execution cost remains very low.