High Rate Matrix Acidizing Technique Using Innovative Diverter Technologies to Restore and Improve Well Performance in North Kuwait Jurassic Gas NKJG
Authors: Ahmed Zamzam , Al-Muhanna Danah , A-Enezi Abeer , Prakash Roshan , Salem Abrar , Mahmoud Wael 
Published: January 2018

NKJG area comprises of eight fields that are structurally complexcharacterized by high pressure & high temperature (HPHT) reservoir properties, critical or near critical nature of the reservoir fluids, high concentration of H2S & CO2 and multiple zones consisting of variations in carbonate formations. Tectonics, as well as the depositional complexities further complicate the trapping and distribution of hydrocarbons, leading the commingled completion and production challenges. Sabriyah field is the second prolific field in NKJG and is divided primarily into two parts; crestal part which is highly fractured and platform part is matrix dominated. Water breakthrough is observed in some of the wells located in the crestal part, and in general, two types of fluids are encountered (gas condensate & volatile oil).

The pilot well where the new diversion technology was implemented is located in the western flank of the Sabriyah field. Limited natural fracturing occur across the 268 ft perforationinterval which is too long for effective stimulation in a conventional "bullheading" approach. Although the permeability is low, vertical permeability distribution ranges widelyacrossthe perforation interval (0.001- 10 mD). Nodal Analysis showed the possibility of tripling the production if all the perforation intervals were stimulated efficiently and contribute to flow. As a result, a sequence of operation was planned which included re-perforation of the current interval followed by stimulation to enhance well performance.

Due to the operational complications, re-perforation was not completed as planned and the well was killed twice with heavy mud causing further damage. As a result, severe formation damage was created leading to significant loss of production, necessitating a robust stimulation treatment. An innovative "High Rate Matrix Acidizing (HRMA)"technique was designed to restore and enhance well production; where a Step Rate Test (SRT) was done prior to injecting main acid treatment to avoid unintended fracturing. In addition, different diversion strategies were usedin combination: one to divert across perforations and the other to divert stimulation inside the formation. All the chemical fluids that used in the HRMA was tested in the lab to confirm its compatibility and solubility with reservoirrock and fluid.

Production was successfully improved after HRMA; where the wellhead pressure, oil and gas rate increased substantially as confirmed by the nodal analysis. During stimulation, there was clear indication of diversion with change in pressure, which confirmed the efficiency of the diverters, and possibility of treating all perforation intervals. Based on the success of this HRMA treatment, similar approach will be used to stimulate other low performers in the North Kuwait Jurassic Gas (NKJG)asset. This paper will provide the details of design, well results, and the overall learnings to address one of the key stimulation challenges in long-perforated deep HPHT wells of NKJG.