Improved Acid Placement Modeling for Matrix Acidizing Optimization

Abstract

Distributed temperature sensing (DTS) data interpretation has been extensively used in the last 10 years for improving acid placement for matrix acidizing operations. The DTS data are used for injection profiling during or after the acid and diverter are pumped into the reservoir. This study proposes an improved treatment schedule option for optimizing matrix stimulation operations with coiled tubing. In addition to the well-established DTS flow-profiling model, the capabilities of the new model include wormhole modeling, acid placement, and skin calculations. Coiled tubing-enabled optical fiber systems are usually used for improving the acid placement during or after matrix acidizing operations. A new model is proposed for designing and optimizing the matrix acidizing treatments in carbonate formations before, during, or after those operations. Specifically, this matrix acidizing model can be used in the pre-planning stimulation stage, before the DTS data is acquired, or during the stimulation, together with or separately from the DTS data. The model can be used in horizontal, deviated, and vertical wells with open-hole or perforated completions. The model takes into account the reservoir data (i.e., permeability, porosity, skin, pressure, and temperature), well data (i.e., tubing and casing sizes, length, number of perforations, etc.), and pumping schedule. Based on the input data and the wellbore hydraulic model, the output consists of the distributed acid rate and volume, wormhole length, and skin factor reduction. The DTS data from a synthetic matrix acidizing operation similar to one performed in an offshore carbonate field is used to validate the new model. An analysis of the results obtained for the previous and improved models is included, identifying the factors affecting the validation. Understanding these factors is crucial, because the new matrix acidizing model has the potential for use in the pre-planning stage with an enhanced acid placement schedule and can reduce operational costs by not using an optical fiber during the stimulation. In addition, the matrix acidizing model can be used during the matrix acidizing operations and can significantly reduce the acquisition time for the DTS data.