The use of coiled tubing (CT) to distribute acid for stimulation has shown good results in the past. Use of CT allows the acid to be delivered evenly throughout the well. This is especially true for openhole wells in which bullheading acid into it will only acidize the heel of the well. While often used, such approaches will create massive enlargements at the entry point where the acid first contacts the acid soluble rock, causing ineffective treatments and re-entry issues. Wellbore collapse often follows. The use of CT as a pinpoint delivery method is therefore preferred.
An even better approach with CT is to add a jetting tool to the bottomhole assembly (BHA). With this configuration, it is an option for different treatments that can be completed in a single trip, such as simple matrix acidizing, acid wash, or even hydrajet assisted acid fracturing (HJAAF). This latter one can be used to place many microfractures or minifractures in the well; and by increasing the bottomhole pressure with annular injection, the HJAAF can create medium to very large fractures for sustained productivity.
This paper discusses the implementation of this combined process in the Middle East. The wells in the discussions have large openhole sections to be stimulated. Moreover, as often found in the brownfields, a small production tubing that has been weakened by corrosion and erosion is present and cannot be removed for many reasons, such as losing the well and related costs. The CT and associated tools in such cases must therefore be very small to enter through this tubing and its associated "no-go" restrictions. A small OD unique jetting mechanism that places the jet nozzles closer to the wellbore wall was therefore necessary to perform this task. Excellent results were obtained using this process and are presented in this paper.