Proving It - A Review of 80 Published Field Studies Demonstrating the Importance of Increased Fracture Conductivity

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMany engineers disregard laboratory reports demonstrating that the pressure losses across proppant samples are substantial. Similarly, it appears that the modeling studies warning of substantial productivity losses due to inadequate fracture conductivity have not been universally convincing.Perhaps many practical frac engineers simply object to the theoretical nature of these arguments, when they quote one of the more influential orators of our time, Shania Twain, 1 stating, "That don't impress me much."Instead, many Petroleum Engineers prefer to see the economic benefit demonstrated in real reservoirs, and seemingly borrow a quotation from the film Jerry Maguire, 2 stating, "Show me the money!"The purpose of this paper is to summarize the results of over 80 field studies where well productivity was improved by increasing the fracture conductivity. The benefit of increased conductivity has been demonstrated in oil, condensate, and gas reservoirs in 50 regions around the globe. This benefit was documented by 250 authors representing over 70 companies. Increased conductivity has been shown to be beneficial in oil wells producing 2 bopd to 25,000 bopd, and in gas wells producing less than 1 MMCFD to over 100 MMCFD. Higher conductivity fractures were proven to improve the cash flow in carbonates and sandstones at depths of 2800 to 20,000 feet, and in low rate coal bed methane wells shallower than 1500 feet.This review of industry experiences in a wide variety of reservoirs is not presented as a substitute for a comprehensive optimization study in a specific location. Instead, the following summary demonstrates that well productivity and profitability can frequently be improved with redesign of hydraulic fractures, despite the failure of many existing production models to predict those benefits.These studies are presented to satisfy the following goals: 1) To verify that the extreme pressure losses observed in the laboratory and predicted by current fluid flow theory are real, i.e., "Proving It". 2) To provide a list of fields, encompassing a wide variety of reservoir types, to assist engineers searching for results from an analogous field. 3) To provide a number of field studies to which production models can be calibrated. 4) To summarize the collective experience of over 250 authors, and incorporate what they have learned into future fracture designs. 5) To demonstrate the relationship between fracture conductivity, well productivity, and cash flow, i.e., "Show me the money!"

Measurement of realistic fracture conductivity in the Barnett shale

“…However, this design parameter tends to be overlooked in shale gas reservoirs. It has been demonstrated that high conductivity fractures are less affected by multiphase flow and may provide benefits in fracturing past condensate blocks (Vincent, 2002). Simulation results also show that low conductivity fractures generate very large pressure drop leading to much less effective fracture networks and lower recovery factor than a high fracture conductivity scenario (Mayerhofer et al, 2006).…”

Field Results: Effect of Proppant Selection on Well Productivity-Cardium Formation

“…Note that the incremental production achieved with superior frac designs was frequently found to be higher than forecast with PredictK. This is not a unique observation; the benefit of fracture conductivity often provides greater benefit than expected 6 . A portion of this benefit may be due to longer effective lengths achieved when fracture conductivity is increased, as has been reported by Barree 7 , and Scott 8 .…”

“…60T, CER, GHC 11.9 (10 6 Figure 6, the averages were calculated from two to nine wells in each category, and suggest that wells treated with ceramics performed the best. The well count for RCS completions is shown to decline because most of these wells are new and have not been producing for a full year.…”

Coalbed methane completions: A world view

“…By analogy, frac designs should be altered for coals N20 mD, but this generally has not been the case, to our knowledge. The issue has been discussed by Vincent (2002), including CBM fracs, and this has led to general recommendations for increasing fracture conductivity in high-perm coals:…”