Design of Fracpack Technique for Medium to High Permeabilty Reservoir

Abstract

Frac pack is a well stimulation technique most suitable to wells with medium to high permeability reservoirs that do not provide commercial production rate even though the formation damage is removed by acidizing treatment or other methods.The term “Pack” is used to emphasize the importance of packing the fracture to gain proppant width or conductivity.A relatively short,highly conductive fracture created in a reservoir of moderate to high permeability will breach near-wellbore damage, reduce the pressure losses & nearwellbore flow velocity/stresses and thus increase the effective wellbore radius.Fracturing treatments in such reservoir consist of two stages : 1)Fracture creation terminated by Tip Screen-out and, 2)Fracture inflation and packing. Such a two stage treatment is the basis of a number of new well completion methods, known as ‘Frac and Pack”.This technique has been successfully applied for a range of fracture sizes in various reservoirs in many parts of the globe. This Frac and Pack is done all in one treatment in one go using specially designed down hole tool.Frac packs are pumped in a single step with screens in place.The gravel pack tool is positioned in a circulating position to provide for seamless transition to gravel pack mode and to provide a pressure measurement on the annulus. Numerous studies indicate that ,when properly executed,this completion technique is statistically superior to all other sand control completion methods used today.In almost every area of comparison,whether in terms of total recovered reserves,flux rate per unit length,longivity,or reliability,it is orders of magnitude better than the closest alternative.In most instances,the enhanced flow efficiencies provide sufficient economic justification to use this method even when alternative cost less to install.This technique is recommended for medium to higher permeability reservoir having simultaneously sand production problems. Although the propped fracturing technology is established for low-permeability formations,the extension of this technology to Soft and permeable formation is still evolving.Frac packing should not be considered a panacea for poor basic completion practices.Sound completion procedures(i.e. filtration and prudent use of kill pills) must be implemented before and after the frac pack in order to realize full production potential. Objective is to study the process and design a Frac pack treatment for sand prone reservoir of medium to high permeability to optimise productivity with particular reference to Western onshore Fields.Under the scope of this work,many studies related to Reservoir formation,sand sampling,Well completion data analysis including field visits & investigations of fracturing works were conducted,followed by some experimentals related to particle size distribution analysis of formation grains, selection of size & shape of grains and propants,screen selection,solubility studies,frac fluid design etc.Analysis of Case Studies of a few selected wells were drawn and observations were made & correlated with various executed wells.This envisages a systematic methology and guide lines towards step by step approaches in implementing Fracpacking technique with suitable remedials to avoid any probable draw backs, for a medium to high permeability reservoir wells of Western onshore fields like Gamij, Jhalora, Bechraji, Santhal, NorthKadi etc.