Predicting and mitigating inorganic scale in XY field

Abstract

Scale is a production problem that occurs in the water system. Scale is a deposit formed from the crystallization and deposition of minerals contained in water formation. The formation of scale occurs due to the incompatibility of the fluid mixture, changes in pressure, temperature, and pH. Generally, scale is formed around perforations, subsurface equipment such as tubing, and on surface production equipment such as wellheads, so that it can result in decreased production rates because the flow of oil from the formation to the surface is hampered. Therefore, it is necessary to make efforts to handle the scale problem, both in the form of preventive and countermeasures when scale deposition has occurred in the field. Preventive measures are preventive measures that can be carried out by using scale control chemicals (scale inhibitors), as well as by maintaining the ionic component of the water that is injected into the well. In this study, the formulation of the problem that will be proposed is how to deal with scale problems that occur in XY field by predicting scale deposits and taking countermeasures through scaling index calculation and literature study which are limited only to reservoir, bottom hole, and wellhead. Through the calculation of the Stiff-Davis and Oddo-Thompson Method, the Scaling Index value is obtained from each scale formed so that it can be seen the types of scales formed in the field. Furthermore, through the Scale Software simulation, the Scaling Index value, the concentration of the formed scale, and the compatibility of the injection water were obtained. From the analysis of formation water through the calculation of the Scaling Index using the Stiff-Davis and Oddo-Tompson methods, it is known that the tendency of the scale formed is the CaCO3, CaSO4 and SrSO4 scales with high positive SI and Is values, with a range between 2.25 to 3.96 of CaCO3, 2.10 to 2.73 of CaSO4, 1.27 to 1.41 of SrSO4. From the calculation of the Scaling Index using the Scale Software, it is also found that there is a tendency to form a scale of CaCO3, CaSO4 and SrSO4 with relatively high values varying from 1.52 to 1.67 of CaCO3, 0.05 to 0.28 of CaSO4, 0.58 to 1.02 of SrSO4. In this XY field, the maximum scale deposits values of CaCO3, CaSO4 and SrSO4, were also obtained, which were 232 mg/L of CaCO3, 410 mg/L of SrSO4, 606 mg/L of CaSO4. From the Scale Software simulation, the scale deposits of CaCO3 of mixing formation and injection waters are lower than the scale deposits of CaCO3 of formation water. Therefore, the injection water is compatible to be injected into the reservoir. From the literature study, the effort to control scale that has formed in the well is carried out chemically, namely through the implementation of acidizing continuously using 15% HCl, (NH4)CO3 water solution, a phosphate-type scale inhibitor, 1500 ppm hydrolysed polyacrylamide, and operate under 1500 psi and 170 deg F.