prior to flowing at a rate of 0.75 million cubic feet per day, the bottonhole pressure was about 800 psia and bottomhole temperature was 247 degrees F. ((Fahrenheit), much higher than the normal 130 degrees F. because of the residual heat from the explosion. Flowing wellhead temperature during the test rose from 68 degrees F. initially to 154 degrees during production at 5 million cubic feet per day and declined to 82 degrees toward the end of production at 0.75 million cubic feet per day. Preliminary calculations indicate that the chimney created by the explosion has a void volume of at least 2 million cubic feet. It is also significant that during the last four days of production at a rate of 0.75 million cubic feet per day the bottomhole pressure increased on the order of 10 to 20 psia indicating that influx into the chimney was greater than the producing rate of 0.75 million cubic feet per day. Field analysis of gas samples collected during the production test shows that the carbon dioxide content of 36 per cent found initially in samples from the chimney continually decreased and hydrocarbons continually increased as expected. The reduction in carbon dioxide, which is thought to have been formed by carbonate minerals decomposed by the explosion, is the result of influx of fresh gas into the chimney. In addition to the test of the emplacement hole re-entry well, a pre-shot well located 300 feet from surface zero was re-entered in June. This well was drilled, using gas, to a depth of 4600 feet after sidetracking at 3691 feet because of damaged casing. After total depth was reached in the gas drilled hole, various logging tools were run for three days. At the end of this three-day period, the well was flowing at a rate of 70,000 cubic feet per day against 54 psia back pressure. Between the time this pre-shot well was recompleted and the time the production test of the emplacement well was concluded, the open hole of the pre-shot well apparently collapsed around the bottom of the tubing, greatly restricting production and preventing testing. Measurements for radioactive constituents of the flowing gas, which was flared and burned, were made continuously during the flow test. As expected, both krypton-85 and tritium were detected by field instruments. The radioactivity levels did not constitute a health hazard to test personnel on the site or the general public off site. 3. Xenon-133 was detected in the field and in laboratory analysis of samples taken in December and January, but none was detected and none was expected in the June-July field analysis because of xenon's short half life of 5.3 days. Detailed analysis of gas samples taken during the flow tests is now under way at the Lawrence Radiation Laboratory, LRL, in Livermore, California. LRL, operated for the AEC by the University of California, provides technical direction for the experiment. Project participants emphasized that the data are preliminary; more refined data and interpretations will be presented at a meeting of the Society of Petroleum Engineers in Houston on September 29. (NOTE TO EDITORS AND CORRESPONDENTS: This announcement also is being issued by the El Paso Natural Gas Company, El Paso, Texas, and the AEC's San Francisco and Nevada Operations Offices.) APPENDIX 10 GASBUGGY PRESHOT SUMMARY REPORT 98-179 O-68-19 Fred Holzer, editor Lawrence Radiation Laboratory Livermore, California November 1967 GASBUGGY PRESHOT SUMMARY REPORT ABSTRACT As part of the Gasbuggy preshot work, two holes, GB-1 and GB-2, were drilled and completed naturally approximately 190 and 300 feet, respectively, from the explosive-emplacement hole, GB-E. The Pictured Cliffs sandstone, extending from 3916 to 4202 ft below the surface, has the following average properties: bulk density, 2.47 g/cm3; compressional velocity, 13,500 ft/sec; porosity, 10%; and water saturation, 58% (4 to 5% water content by weight). The total gas in place is calculated to be 5.8 billion cubic feet (bcf) per 160 acres. When zones having water saturations of 60% or more are eliminated, a net volume of 4.7 bcf is obtained. While core permeabilities average 0.16 md, indicated in-situ permeabilities from buildup tests are between 0.01 and 0.02 md. In GB-1, about 50% of the gas came from a single fracture between 4000 and 4020 ft deep, and most of the remainder came from bedding planes in the Fruitland zone, between 3800 and 3882 ft. In GB-2, most of the gas came from a fracture near the top of the Pictured Cliffs. In view of the complex flow pattern, values of reservoir characteristics derived from flow tests must be considered apparent only. We expect the 26-kt nuclear explosion at the base of the Pictured Cliffs to create a chimney between 330 and 400 ft high with a radius of 78 ft. Fracturing should extend radially about 400 ft. No flooding of the chimney with water is expected. The chimney gas is expected to contain about 200 μC of tritium and 2 μC of Kr85 per cubic foot of gas at normal temperatures and pressures. Rapid flaring of three chimney volumes might reduce these concentrations by a factor of ten. INTRODUCTION This is a report on the status of the Gasbuggy experiment as of September 20, 1967. Gasbuggy will be a nominally 26-kt detonation at a depth of 4240 feet; its purpose is to determine to what extent an underground nuclear explosion can stimulate the production of natural gas from low-permeability formations. Almost all the preshot field work has been completed, and most of the data have been reduced though not all have been analyzed. Detailed plans for programs at the time of the shot are essentially complete, and hardware for the dynamic measurement instrumentation and the deviceemplacement system has been manufactured. The objectives of the Gasbuggy experiment are: 1. To measure the changes in the deliverability and ultimate recovery of the gas and to identify the mechanisms responsible for these changes; |