Relative Permeability Modifier Preflush Fracture-Stimulation Technique Results in Successful Completion of Previously Bypassed Intervals

Abstract

A fracture-stimulation technique that includes an in-situ gener- ated relative-permeability modifier (RPM) preflush has been used to tap previously bypassed reserves in an Argentina forma- tion. The formation was reported to have high water-saturation levels. Fracture-stimulation treatments performed in similar intervals usuallyintersect a stringer of water within the targeted interval, orextend into the highly saturated areas above and/or below the interval. Water cuts as high as 60 to 70% have made production of such intervals uneconomical. A major operator has used the new RPM polymer-based preflush (PBP) technique on more than 15 wells in an Argentina formation. Data gathered from the first 3 months of production economically justify the stimulation treatments. In many cases, the treatment has limited water production to less than 15%, and some applications have reduced water production to negligible levels. This paper discusses the job design, field application, and results of several RPM preflush treatments performed in this area between 1997 and 1999. Introduction Controlling water production has been an objective of the oil industry almost since its inception. Produced water has a major economic impact on the profitability of a field. Producing 1 bbl of water requires as much or more energy required to produce the same volume of oil. Often, each barrel of produced water represents an equal amount of unproduced oil. In addition, water production causes other problems, such as sand production, the need for separators, disposal and handling concerns, and the corrosion of tubulars and surface equipment. The reflective analysis of lifting water is normally based on a barrel of oil equivalent (BOE) cost. This value reflects the cost of the energy required to lift sufficient produced fluid to gain 1 bbl of oil. BOE is calculated from the total energy costs required during the production of all fluids divided by the barrels of oil actually produced. The profit obtained from the well is deter- mined by the BOE subtracted from the selling price of the oil. All other overhead expenses are paid out of the remaining profit. For several years, research has been dedicated to the devel- opment of chemical systems that can selectively reduce water production without reducing oil production. 1–4 Initially, two methods were used to reduce water-production problems:produced water was separated from the oil for disposal, ora plugging agent was squeezed into the formation to stop water entry. However, because these methods were designed to stop water production, they often curtailed oil production and/or damaged the formation. Early conformance chemicals intro- duced to decrease the water-oil ratio (WOR) of the formation werewater-reactive agents that selectively plugged water- filled pore throats, andchemicals that increased water viscos- ity, thereby impeding its mobility while only minimally altering oil production. Polyacrylamides (PA(tm)s) have been used with this technique with only limited success.5

Challenging the Economic Limit in Mature Fields by Hydraulic Fracturing of Wet Producers

“…The VDPMs have been successful in a number of fracturing applications as the fracturing fluid or as a prepad to limit water production when treating layered reservoirs with widely different water saturations or formations with a known OWC. This practice started in the late 1990s with the use of low-viscosity RPMs as a preflush before hydraulic fracturing treatments (Brocco et al 1999;Brocco et al 2000). In other cases, the RPM polymer was included as an additive in the conventional fracturing fluids (Dos Santos and de Melo 2005).…”

Relative-Permeability Modifiers Used in Conjunction With Hydraulic Fracturing Can Increase Hydrocarbon Production and Reduce Water Production

“…In the mid-1990s, RPMs were introduced as a prepad fluid in hydraulic stimulation treatments in areas where breaking into nearby water zones commonly occurred. The results of this application significantly reduced postwater production after hydraulic stimulation treatment, and allowed operators to treat and produce previously bypassed formations (Brocco et al 2000;Fry et al 2006;Torres et al 2006).…”