The first application of controlled crack height acid-frac stimulation technique in the Missan Oilfield of Iraq

The reservoirs in the Missan oilfield are mainly carbonate reservoirs, and some wells have poor reservoir properties. Conventional matrix acidification measures cannot guarantee increased production and stable production, so acid fracturing production enhancement measures need to be considered. The main goal of acid fracturing transformation in Missan Oilfield is to develop acid etched fractures that are relatively long and have a certain flow capacity. The horizontal section of the A well is 656.5 meters long and only 15-18 meters away from the water layer. To ensure the effectiveness of acid fracturing while avoiding communication with the water layer, high acid fracturing technology with controlled fractures was adopted for the first time. The fracture height was controlled by reducing the displacement, lowering the viscosity of the pre fluid, initiating fractures with low displacement, and increasing the displacement step by step. Two clusters of fracturing acid fracturing operations were carried out on the horizontal bare eye section that has been drilled into the borehole, with a fracturing acid volume of 400 m³ per cluster. In the case where the fracture diversion capacity is equivalent to that of conventional acid fracturing design, the average fracture height decreases from 31.6 m to 19.4 m, with a reduction of 38.6%. The closest distance to the water layer increases from the average value of 1.6 m in conventional design to the average value of 10.4 m controlling fracture height, an increase of 5.5 times. After 2 months of operation, the average water content of Well A gradually decreased from 26.5% to 0.5%, with a cumulative oil production of 1.71×10⁴ m³, achieving a good effect of increasing production and avoiding communication with water layers. The boundary conditions for using acid fracturing technology in this oilfield were explored, expanding the application scope of this technology.