Productivity Performance Comparisons of High Rate Water Pack and Frac-Pack Completion Techniques

Abstract

Recently, advances in sand control completion practices have lead to the evolution and popularity of two different completion techniques: the high rate water pack (HRWP) and the frac-pack. A wealth of information has been published regarding each separate completion technique, but little information has been published on the direct comparisons of the two techniques. This paper describes three cases, from three separate fields, in which the HRWP and frac-pack techniques were employed. In each case, a completion was performed in formations with similar reservoir characteristics utilizing both the HRWP and frac-pack techniques. Completion steps for both the HRWP and frac-pack wells are discussed at the end of this paper. Production performance from each example is compared, as well as results from bottomhole pressure transient tests. System analysis is used in each case to compare completion effectiveness. The results are summarized with a brief economic evaluation of the two completion techniques for each case history. All three of the example sets presented in this paper consist of high permeability gas-bearing sands located in the Gulf of Mexico. Each example completion is from an area known to produce sand in large quantities if a successful sand control treatment is not performed. Introduction The examples that follow contain a brief description of the wells to be compared, along with a general description of the wellbore configuration and initial flow rates. A more detailed description of the frac-pack and HRWP completion techniques can be found at the back of this paper (Attachments 1 and 2). Table 1 contains the wellbore geometry and reservoir flow parameters for each case discussed in this paper. A comparison of well performance based on production rates, as well as a comparison of bottomhole pressure build-up data, is included for each well. In each gas well used in the following comparisons, a multi-rate test was performed in order to determine the turbulent coefficient associated with each completion. The analysis of the turbulent coefficient for each case history yielded interesting results. However, more conclusive results were drawn when the turbulent coefficients were compared by completion type. A brief discussion on the -system analysis results and potential productivity gains associated with each completion technique is included. Finally, a net present value (NPV) calculation was performed on each completion based on the cost associated with the completion, the production rates seen by each well and the forecasted production for each well. Capital expenses and first production were assumed to occur in June 1997. Expenses were forecasted based on each field's historical operating costs. Product prices were assumed to average $1.81/Mcf for 1997, $1.88/Mcf for 1998 and $1.92/Mcf for 1999. All net present values discussed in this paper will be discounted at 15%. A summary section will provide an overview of the data presented in an attempt to draw guidelines for selecting a completion technique of choice in sand control situations, based solely on deliverability. Other design considerations that are not discussed in this paper are the relative location of nearby fluid contacts (oil/gas, water/gas or water/oil), down hole equipment limitations and the dependability of the completion to control sand production. P. 269^

A New Methodology To Safely Produce Sand-Controlled Wells With Increasing Skin

“…The laboratory data by Welling also showed that if gravel is mixed with sand, as can be the case with poor displacement of formation sand from the perforations by gravel during a gravel pack, the effective permeability of the gravel sand mixture easily can be only 10% of the original gravel permeability. Powell et al (1997) used pressure-transient testing to show that both the Darcy and non-Darcy skins from frac-pack completions were significantly lower than those of high-rate water-pack completions (a variation of gravel packing). While the frac pack can increase fracture length and then possibly yield a negative skin, pressure-transient testing rarely exhibits a negative skin for frac-pack completions.…”