Commingled Production Experiences of Multilayered Gas-Carbonate Reservoir in Saudi Arabia

Abstract

Saudi Aramco employed extensive matrix and acid fracturing treatments in thedevelopment of Saudi Arabian non-associated gas carbonate reservoirs.Thetarget reservoir is the Permian Khuff Formation which is the majornon-associated gas reservoir in the prominent Ghawar Field, eastern SaudiArabia.The Khuff reservoir is stratigraphically divided into fourcorrelative zones, namely Khuff-A, B, C, and D in downwardsequence.Khuff-B and C are the two major reservoirs with distinctivehydraulic characteristics. Khuff-A and D zones mostly are either discontinuousor have poor to non reservoir quality. Saudi Aramco is pursuing commingled production selectively as a part of thegas development plan to extend the well's economic life and to meet its growingdomestic gas needs. Since the Khuff-C has better reservoir quality with larger gas reserves, itwas completed by itself during the initial period of the fielddevelopment. Later, the commingled production by adding the Khuff-A and Bhas become part of the overall strategy to offset the natural decline fromKhuff-C and maximize gas production and extend the wells' life. This paper will review the acid fracturing and stimulation practicesemployed by Saudi Aramco in the Khuff-Carbonates. The criteria used to selectsuitable candidates for the commingled production and techniques employed toquantify flow contributions from each individual zone after commingling theproduction will be reviewed. The production performance, lessons learned, business impact and the way forward will be discussed. Introduction Since 1995, Saudi Aramco has embarked on an aggressive non-associated gasreserve development program and gas expansion projects.These projectsencompass the drilling of new wells and developing new reservoirs wherevercommercial gas reserves can be found. Developing the Permian Khuff-Carbonate reservoirs in the prominent GhawarField, eastern Saudi Arabia (Fig. 1) is in the center of this ambitious programto address the ever- increasing domestic energy requirement. Saudi Aramco employed extensively acid fracturing and high rate matrixacidizing stimulations to exploit the Khuff gas reserves. More than 200 Khuffgas wells hydraulic fracturing stimulations have been successfullyemployed. Saudi Aramco is pursuing commingled production selectively as a part of thegas development plan.Through case history examples, this paper will shedlight on the deployed stimulation practices, commingled production results, lessons learned, and business impact.

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