This paper presents the basic methodology for real-time evaluation and execution of hydraulic fracture treatments and attempts to address some of the current perspectives about the subject. It is important to realize that only a small part of real-time hydraulic fracturing is model specific. The brunt of this technology is encompassed in the techniques used to optimize the diagnostics and actual execution of the fracture treatment.
A precise methodology for performing real-time evaluation and execution of hydraulic fracture treatments is discussed. Recommendations are provided to specifically tailor the design of the pre-treatment diagnostic injections to the wellbore geometry, reservoir, and fracturing characteristics. From these diagnostic injections stages, critical fracturing mechanisms such as perforation friction, near-well bore tortuosity, leakoff, fracture geometry, multiple fracturing, closure stress, pipe friction, etc. can be determined. The important consideration is that the engineer be trained to take a methodical approach to ensure the diagnostics acquire the desired information. Too often today, diagnostic injections are executed without any consideration for wellbore or formation characteristics and are consequently, in many cases, ineffective.
Once these diagnostic injections are evaluated, the treatment is re-designed based upon the actual fracturing character of the formation. It is virtually impossible to predict how a reservoir will hydraulically fracture without first pumping into the interval.
Real-time evaluation and execution reaches the pinnacle of technological use during the actual pumping of the fracture treatment. A variety of modern techniques exist to continue the characterization of the fluid and fracture to minimize risk of premature screenouts and optimize the proppant distribution within the fracture.
Real-time hydraulic fracturing was first introduced in 1986 and has been successfully established through many successful case histories. In general, real-time evaluation and execution involves the collection and interpretation of hydraulic fracture treatment data while the treatment is in progress. Through a series of pre-treatment diagnostic injections and co-treatment execution techniques, the fracturing character of the rock is diagnosed and subsequently addressed allowing the treatment to be optimized. The overall approach is interactive, with the engineer determining the diagnostic design, data analysis technique, fracture model and evaluation criteria.
Since the beginning of this modem technological evolution, many technical papers have specifically discussed various real-time data acquisition and analysis methods. New methods for determining fracture closure pressure in both the pay interval and adjacent layers have been developed. Several papers have been presented for characterizing the near-wellbore fracture geometry components and addressing them during the fracture treatment. History matching of the actual pressure response allows tangible determination of the fracture geometry and leakoff response so the treatment can be re-designed quickly based on the actual fracturing character of the rock. Recently, the recognition of multiple far-field fracture propagation has resulted in the development of predictive models and methods for remediating and addressing these complex fracture geometries.
Aside from the actual mechanistic aspects previously mentioned, probably the most fascinating part of real-time execution is the integration of all data that allows every variable, either raw or calculated, to be tracked, in real-time, without processing delay. The fracture treatment response can be represented on any graph type, scale and/or with any variable. This allows a level of scrutiny of what is occurring during a job that has never before been available. The "catch 22" is that specific training, expertise and experience are necessary to achieve full benefit using this modern technology because of the fast moving process that occurs during the execution of any fracture treatment. The fracture entry character of a fluid type or proppant concentration can be observed with high resolution graphics early in the treatment, providing information on how the rock is fracturing. Associated improvements can be made to remediate pre-mature screenouts and optimize proppant distribution. P. 117^