Optimizing the Profitability of Matrix Acidizing Treatments
Authors: Vogt T.C. , Anderson M.L. 
Published: December 2007

Described here is a mathematical model for optimizing the profitability of matrix acidizing treatments for both oil and gas wells, with or without prorationing. The model allows its user to determine whether the economic prorationing. The model allows its user to determine whether the economic potential of an unstimulated well can be increased by acidizing and to potential of an unstimulated well can be increased by acidizing and to select the most profitable treatment design from a number of alternatives.

Introduction
Over the years, well stimulation research has concentrated mainly on developing advanced matrix acidizing, and fracturing techniques, with less attention given to economic optimization of such treatments. We describe here a mathematical model for optimizing profitability of matrix acidizing treatments for both oil and gas wells, with or without prorationing. This model, in essence, allows its user todetermine whether the economic potential of an unstimulated well can be increased by matrix acidizing andselect the most profitable treatment design from a number of alternatives.
Maximum present worth (with the discount rate specified by the user) is the criterion for optimum treatment design. As an alternative, the user may, for instance, maximize the ratio of present worth to treatment cost. Either way, the model analyzes cash flow on an after-tax basis and takes into account all relevant costs, royalties, and depletion and timing effects, as well as the effect of wellbore damage or previous stimulation. Other advantages of this model are thatwell production rates can be increased as a result of more production rates can be increased as a result of more efficient treatment design,treatment costs can be reduced when acid reactivity is a limiting constraint on treatment size,the most profitable cases can be selected from among a number of wells that could be profitably treated,unprofitable treatments can be identified, andworkover budgets can be more easily formulated.

General Scheme
The profitability of matrix acidizing treatments is determined using relationship between stimulated well performance and treatment size (cost). The present worth for a given well can be calculated for present worth for a given well can be calculated for a given acid formulation as a function of acid volume. For hypothetical treatments using small volumes of acid, the predicted improvement in production capacity (and present worth) increases rapidly with small incremental increases in treatment volume. At some point, increasing the acid volume no longer provides sufficient improvement in well productivity and the present worth decreases from its maximum. The present worth decreases from its maximum. The optimum treatment represents a level of stimulation severity at which the last increment of cost earns a rate of return equal to the discount rate (Fig. 1). The model presented here equates maximum present worth with economic optimization; however, the economic indicators of the total project for example, discounted cash flow rate of return, incremental reserves due to stimulation, profit ratio, and payout are calculated to provide the basis for a decision on whether or not to stimulate the well.

Assumptions
Assumptions used as a basis for the model are listed below. These conditions do not limit the analytical scheme and can be modified by the user to accommodate the latest stimulation technology. 1. Acid penetrates the matrix uniformly and radially.
JPT
P. 1055