Optimization Chemical Acid Stimulation by Improving Selection Intervals in Lateral Section of Horizontal Well in X Field Heavy Oil Steam Flood

Abstract

Abstract The production of horizontal wells in X field has decreased since 2019-2021 at a decline rate of 40% per year. Therefore, it is essential to increase production of horizontal wells through proper and effective jobs. The decreased production rate of the horizontal well due to plugging by CaCO3 scale in the wellbore along the lateral part of the horizontal well. It is because during the process drilling horizontal well using a fluid loss additive in the form of CaCO3 to prevent total loss circulation. To eliminate the problem of plugging scale along the lateral section of the horizontal well, chemical acid stimulation job is required. Some chemical stimulation jobs on horizontal well have been carried out, such as acid bullhead, solvent bullhead, and chemical acid CTU (Coiled Tubing Unit). The chemical bullhead work in 2020 is less effective on horizontal wells because it cannot reach the right target on the lateral section of the horizontal well. In 2020 there were 20 CTU chemical acid of horizontal wells were stimulated in all lateral areas even though there were areas that had low resistivity values because the wells penetrated the shaly sand. This has resulted in the ineffectiveness of the acid treatment area on the lateral section resulting in a low average oil gain of 2 bopd/job and a low success rate of 40%. It is caused by two factors, methods, and materials. The first factor is methods due to horizontal wells were stimulated in all areas section of lateral horizontal even though there were areas that had low resistivity values. It caused some of volume chemical acid treated at improper zone in lateral section of horizontal well. The second factor is materials due to HCl15% didn't effective working properly at immature reservoir. This paper shows how to improve two main factors that caused low oil gain and failures job of previous acid CTU in horizontal well. The improvement process must solve both two factors caused failed acid CTU jobs. The first improvement for the factor method by selecting intervals only for zones which have resistivity above 10 ohm and no found cross over between Neutron and Density log. The second improvement is to ensure that reservoir is mature (hot) for candidates of chemical acid CTU horizontal well to ensure that oil will flow from reservoir to wellbore. By improving selection process of chemical acid CTU in horizontal wells, it successfully achieves to improve oil gain from 2 bopd/job to 28 bopd/job, success ratio increased 40% to 98% and decline rate of oil production horizontal well 40%/year to incline rate 14%/year. Besides that, this improvement process success to deliver actual financial benefit about $US 4 MM. The new smart method for selecting effective area in lateral section of horizontal well successfully significantly improve result of oil gain and success ratio in performance of stimulation acid job using coiled tubing in horizontal well.