This paper was prepared for presentation at the 1999 SPE/EPA Exploration and Production Environmental Conference held in Austin, Texas, 28 February-3 March 1999.
SPE Members Abstract This paper presents a foundation and methodology for real time three-dimensional hydraulic fracturing simulation and analysis. The equations governing fracture propagation are summarized for both rate and net pressure boundary conditions. A new dimensionless pressure slope parameter Is introduced which prevents using chaotic measured or calculated pressures. This parameter also helps identify near wellbore restrictions. The real time fracturing simulator utilizes the same numerical modules and routines as the design program. This will insure design, real time and program. This will insure design, real time and post-design simulation compatibility. Simulated post-design simulation compatibility. Simulated results for the rate and net pressure driven models can be displayed concurrently during the hydraulic stimulation. Comparative studies of the rate and net pressure driven numerical results are included. A posttreatment analysis of a real time field case study posttreatment analysis of a real time field case study is presented to illustrate the application of this real time fracturing system. The importance of using a dimensionless pressure slope is also discussed. Introduction During the 1980's on-site monitoring of the hydraulic fracturing process evolved to new levels of sophistication through the use of on-site computers. This enabled the operator to perform numerous analyses and fracture diagnostics during stimulation The operator no longer had to rely on strictly digital data but was now able to view the fracturing process graphically. When such monitoring systems were coupled with skid technology detailed pumping and blending quality control analyses were possible. The information provided by such monitoring systems began to impact provided by such monitoring systems began to impact the decision making process on-site and on future treatments. The process monitoring capabilities of on-site computers with skid units has proven to be a useful and cost effective application of technology. Currently on-site computers are used for monitoring, quality control analyses, pressure diagnostics and real time fracture simulation using rate and pressure driven 3-D models. A description of the hardware/software and real time hydraulic fracturing simulator is discussed below. A number of comparative studies between the rate and pressure driven solutions are presented and illustrate the similarity of numerical results. Finally, a real time field example is shown for the rate and pressure driven solutions. DESCRIPTION OF HARDWARE/SOFTWARE AND FRACTURE MODEL Hardware and Software The on-site monitoring and fracture software is designed to run on a 80386/80486 IBM compatible computer. The system requires four megabytes of memory, a math co-processor, hard disk, VGA graphics and an RS-232 communications port. This hardware configuration is commercially available on many laptop, portable and desktop models. A printer can also be used to allow real time printer can also be used to allow real time digital and graphical output to be down-loaded during monitoring. The system is portable and can be easily interfaced by a common RS-232 interface. The system can be interfaced to another computer such as a service company monitoring system or be interfaced to a data acquisition system for independent transducer monitoring. P. 417
Using a two-stage screening procedure, ICD-9 diagnostic criteria, and the Hamilton Rating Scale for Depression, the authors diagnosed depressive disorders in 81 (9.2%) of 881 patients in a primary care setting in Kenya. All depressed patients had somatic symptoms, and all of the 27 depressed patients assessed with the Hamilton scale scored higher than 2 on the work and activities item. These findings contradict the earlier reports that Africans do not admit to being depressed. Nearly one-third of the depressed patients were moderately or severely ill and would have benefited from psychiatric assessment and treatment.
In 1979, methods were established for analyzing formation properties before a hydraulic stimulation (prefracturing test) and for interpreting fracturing pressure behavior during treatment (slope analysis). These methods were used as a basis in writing software for an on-site computer system. Since 1980, this system has been used for prefracturing test analyses (in the form of step rate, flow-back, and pressure decline tests) and for monitoring hydraulic fracturing treatments (in the form of real-time graphics of surface parameters and downhole pressures).This information was then applied to improving quality control and job design.
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