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Abstract Recent (companion) publications have isolated some major new conclusions which have effectively led to reversal of many conventional practices in hydraulic fracturing: these conclusions are based on analysis of field data vs. erroneous theories which had influenced previous efforts. A prime example of such reversal is our conclusion that overall proppant concentration (i.e. total proppant over total fluid volume pumped) should vary essentially inversely with reservoir permeability. Other issues have been demonstrated by recently-published case-studies of fracturing in low-permeability reservoirs. This paper will extend that discussion to medium-high permeability applications, i.e. to gas (oil) reservoirs of order 1-10 (10-100) mD or more. This paper will also emphasize many major unrealized and/or poorly-rationalized aspects of such fracturing operations: these will include identification and execution of adequately-packed fractures ("pack-fracs" vs. common near-wellbore "frac-packs"); related work has quantified the dominant role of permeability variation in fracture growth/geometry. It will be indicated that many of the common/expensive problems associated with correspondingly mal-designed/executed field operations may be easily remedied: primary among these concerns are premature screen-outs/wash-outs and proppant production problems. This paper will also demonstrate the tremendous (incremental) economic benefits of fracturing most wells, especially where variable petroleum demand/price have made capital investment decisions difficult (and often foolish, at least in retrospect). Appropriate use of the right technology also serves to reduce (correctly/actuarially - accounted) risk, certainly when properly executed to avoid the common problems which have plagued previous experiences; proper execution should also serve to remedy unfulfilled claims/promises, which have previously hindred widespread hydraulic fracturing technology application. Reliable fracturing capabilities now create major new (overall project) options for/and greatly improved investment strategies. Introduction Common application of hydraulic fracturing in medium-high permeability reservoirs has taken place only in the past decade, despite extensive application to lower-permeability reservoirs over the past three or four decades (e.g. Refs. 1-4); such high-permeability applications (e.g. Refs. 5-10) have been driven by special needs, e.g., to solve problems and/or make existing projects (more) economically attractive - as opposed to required use in lower-permeability environments, where the most "experience" has been gained. Ironically, success in medium-high permeability applications has been substantially more consistent: the reality (Refs. 11-22) of results obtained in lower-permeability operations requires much more careful (statistical) evaluation over a broad range of environments, especially since the key parameter (kH) is more amenable to manipulation, with limited/questionable data (e.g., conventional well-test analysis). Extensive investigations over the past decade, both in the laboratory (Refs. 11,12), and mostly in the field (e.g. Refs. 13-22), have led to comprehensive re-evaluation of the principles and methodology for design, execution and evaluation of hydraulic fracturing treatments. New effective field methods have been emphasized/implemented, but mainly for lower-permeability applications (Ref. 22); they are being gradually extended into the higher-permeability domain (e.g. Ref. 21), in order to explain (and then greatly improve) various "successful" experiences already reported in that forgiving context (e.g., Refs. 5-10). This paper will emphasize five major aspects of understanding required to successfully/optimally execute appropriate (fracture) operations, especially in higher-permeability environments:Five dominant (fracture) issues exposed over the past decade;Simple (True PI) basis for evaluating (fracture) performance;Simple (RoI) basis to evaluate overall economic success;Selected illustrative case-studies of hydraulic fracturing; andAdditional realized/potential benefits of proper fracturing. Implications include whole new well technology/methodologies. |
