Abstract
Acid injection is a concept to stimulate carbonate reservoirs by removing damage caused during well construction operations. The most common form of this treatment is matrix acidizing. An emerging technology involves the use of needles in a multilateral fishbone completion (known as fishbones), which are installed by injecting acid at high velocity. The design of acidizing operations is complex, depending on variables such as rock characteristics, operational conditions, and thermodynamic conditions. Consequently, a sophisticated modeling approach is required to accurately predict and optimize the operation of fishbone treatments. The mathematical formulation of the model involves solving differential equations for flow in porous media, acid transport, and wormhole propagation. Wormhole propagation is based on Pore-volume to breakthrough tests (PVbt), typically performed at laboratory to characterize the rock-fluid behavior in acidizing operations. In this work, experimental tests were performed to support the numerical developments. Comparative results from lab measurements and modeling are presented with good agreement. The model is then applied to simulate typical field operations. The movement of the fishbone needles during their installation is represented by varying the acid injection point over the simulation time. Details of the finite element mesh built for the simulations are discussed, and examples of vertical and horizontal well simulations are presented in this paper. Moreover, the continuous acid injection after the needle installation is evaluated, indicating additional productivity gains.
