Commingled production experiences of multilayered gas-carbonate reservoir in Saudi Arabia

Saudi Aramco employed extensive matrix and acid fracturing treatments in the development of Saudi Arabian non-associated gas carbonate reservoirs. The target reservoir is the Permian Khuff Formation which is the major non-associated gas reservoir in the prominent Ghawar Field, eastern Saudi Arabia. The Khuff reservoir is stratigraphically divided into four correlative zones, namely Khuff-A, B, C, and D in downward sequence. Khuff-B and C are the two major reservoirs with distinctive hydraulic characteristics. Khuff-A and D zones mostly are either discontinuous or have poor to non reservoir quality. Saudi Aramco is pursuing commingled production selectively as a part of the gas development plan to extend the well's economic life and to meet its growing domestic gas needs. Since the Khuff-C has better reservoir quality with larger gas reserves, it was completed by itself during the initial period of the field development. Later, the commingled production by adding the Khuff-A and B has become part of the overall strategy to offset the natural decline from Khuff-C and maximize gas production and extend the wells' life. This paper will review the acid fracturing and stimulation practices employed by Saudi Aramco in the Khuff-Carbonates. The criteria used to select suitable candidates for the commingled production and techniques employed to quantify flow contributions from each individual zone after commingling the production will be reviewed. The production performance, lessons learned, business impact and the way forward will be discussed.