X reservoir in one of Iraq's field, is a medium pore, low permeability and small pore throat limestone oil reservoir with poor petrophysical characteristics. This reservoir group in which X reservoir is in constitutes to about 20% of the total resource in place. Conventional development allows only about 0.3% of reserves to be developed and this needed to be improved further. The mixed results of various stimulation campaigns (for example matrix acidising and acid fracturing) carried out earlier for this reservoir has prompted the Operator to evaluate the hydraulic fracturing stimulation, first of its kind in Iraq to further gauge its effectiveness and feasibility for field implementation.
This paper will discuss the steps undertaken before, during and after the hydraulic fracturing execution. In planning for this campaign, steps were taken to analyse the rock properties and mechanics of the formation to understand the challenges for the hydraulic fracturing and to enable optimisation of the fracturing parameters. Fracture fluid design, proppant optimisation and treatment design were proposed to systematically optimise the process of the hydraulic fracturing. As a deduction, the principles and recommendations of design optimisation for hydraulic fracturing in carbonate reservoirs will be presented in this paper.
The preliminary production gain from this pilot hydraulic fracturing exceeded the pre-job stimulation more than 10 times, showing promise of a new way of developing this challenging reservoir in the future. Comprehensive analysis of the reservoir characteristics and suitable fracturing design are key to this achievement. This approach will be the benchmark for future hydraulic fracturing jobs planned in the field. The optimisation study in this paper could serve as a reference to improve hydraulic fracturing efficiency and success in other similar carbonate reservoirs.
Being the first ever hydraulic fracturing campaign ever performed in Iraq, this paper will focus on the challenges, execution and preliminary results.