An Approach to Identifying the Optimal Time to Initiate Stimulation Operations

Abstract

This research describes the application of a production economic approach which attempts to quantity stimulation treatments performed on different wells undergoing a decline phase in  their production and to obtain based on the output from the model the best time during the declining phase of the wells to initiate stimulation treatments.

Two different production decline models were considered in this work i.e., the exponential model and the hyperbolic model.

The optimization models which are in the form of non-linear programming models combine production decline curve analysis with economic discounting concepts.

The objective function of the non-linear programming problem is subject to the constraints imposed by the production facilities, reservoir productivity and the stimulation budget approved by management.

The results from both optimization models show that the best time to  initiate  stimulation during the decline phase of a wells production should be during the periods when the current production rate is at least fifty percent of the initial production rate.

The optimal discounted production for the exponential model shows that the best time to initiate stimulation is when  the wells current rate is about seventy percent of the initial production rate.

Introduction

Background Of Study

Well stimulation is being utilized throughout the world in an attempt to increase oil and gas production rates by maximizing reservoir energy, increasing the effective wellbore radius, increasing permeability  and conductivity around the near wellbore, and recently in Enhanced   Oil Recovery (EOR) processes.

It is one aspect of well construction operations that has attracted a lot of research and publications over the years because of its scope and the fact that the operation increases the production of petroleum from the reservoir.

This increase in production is  achieved  by  removing the damage around the wellbore or by superimposing a highly conductive structure onto the formation.

Several well stimulation techniques have been used; the commonly used processes include hydraulic fracturing, recompletion, matrix acidizing and fracture acidizing.

As with many engineering processes, stimulation must culminate in the design, selection of the specific treatment and, of course, selection of candidate wells.

To choose among the various options, of which one is to do nothing, a means for an economic comparison of the incremental benefits weighted against the costs is necessary ¹

Hence it is important to select stimulation candidate wells that have potentials for maximum benefit.

Candidate Selection is the process of identifying and selecting wells  for  treatment  which have the capacity for higher production and better economic return.

Thus, in stimulation candidate well selection, the treatment yielding the highest discounted rate of return is the treatment which, in principle, should be carried out first.

References

Economides, M.J., and Nolte, K. (eds.), Reservoir Stimulation (2nd ed.), Prentice Hall, Englewood Cliffs, NJ (1989).

Peter Valko., Lewis Norman.,& Ali A. Daneshy “Well Stimulation,” in Economides, M. J. & Nolte, K. S., (eds.), Reservoir Stimulation, Schlumberger Education Services, Houston, Texas, 1987

Balen, R.M., Meng, H.Z., and Economides, M.J.: ‘‘Application of the Net Present Value (NPV) in the Optimization of Hydraulic Fractures,’’ paper SPE 18541,

Civan, F.: Reservoir Formation Damage – Fundamentals, Modeling, Assessment and Mitigation, Gulf Publishing Company, Houston, Texas (2000) 1

Bennion, B., “Formation Damage—The Impairment of the Invisible, by  the  Inevitable and Uncontrollable, Resulting in an Indeterminate Reduction of the Unquantifiable!” Journal of Canadian Petroleum Technology, Vol. 38, No. 2, February 1999, pp. 11-17.

Energy Highlights, 1990