The objective of many matrix acidizing treatments in the Khuff carbonate formations is to remove drilling damage and enhance productivity after the drilling process. Open hole and multilateral completed wells, present several challenges that prevent an optimum intervention with coiled tubing (CT). Traditional practices have been limited to spot stages of pre-flushes, acid, and diversion systems in front of the formation from toe to heel without proper control over the placement process.
Using an innovative workflow, interpretation of distributed temperature surveys (DTS) responses, correlated with reservoir data, assists in selectively placing fluids, maximizing the contact of stimulation fluids with the targeted formation sections. Two field applications, in dual-lateral horizontal open hole gas producers, that demonstrate how to optimize a stimulation treatment as it occurs, were implemented in a field in the Kingdom of Saudi Arabia.
In both cases, selective access to pay zones in each lateral was confirmed with DTS profiles. Following the pre-flush and the first acid pass, DTS measurements indicated acid effect over the permeable zones but also detected fluid movement towards non gas bearing thief zones. Foam and energized visco-elastic diverting acid fluids were used to divert acid to the target zones avoiding the lost of all stimulation fluids to the toe in one case and to the heel in the other well. After treatment, the gas production increased from zero to more than two times the expected rate in both wells.
Understanding of the flow patterns as fluids are placed in the wellbore was possible. Changes to the fluid placement schedule during the job resulted in optimum acid coverage and efficient diversion confirmed by the downhole measurements. The identification of the thief zones was critical to avoid wasting fluids. This experience, the first ever gas wells in Middle East, represents an opportunity for un-locking production potential in similar gas developments.