Long-term Pumping Test Research Articles

On the origin of saline fluids in the KTB (Continental Deep Drilling Project of Germany)

Highly saline fluids were encountered during the German Continental Deep Drilling Project (KTB) from depths ranging between 2 and 3 km to about 9 km. The most reliable data were obtained from samples extracted during a long-term pumping test in the 4000-m deep KTB pilot hole. Some 460 m 3 Ca–Na–Cl brines with about 68 g l −1 total dissolved solids (TDS) and some 270 m 3 associated gases, mainly N 2 and CH 4 were pumped to the surface from the main fracture system situated near the bottom of the pilot hole. Geochemical and isotopic data support the hydraulic tests which suggest the presence of an open and large fluid reservoir at depth. The pumped fluids from this main fracture system were released from a deep reservoir situated at more than 5500 m depth which is hydraulically connected with the 9101 m deep KTB main hole, drilled some 250 m to the northeast of the pilot hole. While Ca and Sr contents of the extracted brines may be the result of water–rock interaction, Cl is most likely of external origin. The Cl is hypothesized to derive from geotectonic processes rather than to descending infiltration of paleo-seawater (evaporitic brines). The sampled fluids have probably migrated from a deeper reservoir to their present position since the Cretaceous–Tertiary period due to tectonic activity. However, several isotopic studies have identified an admixture of descending paleowaters down to more than 4000 m depth. The high 36Cl/Cl ratio of the fluids sampled during the long-term pumping test point to a host rock highly enriched in U–Th, unlike the sampled KTB country rocks. The fluid reservoir is believed to be in contact with the Falkenberg granite massif situated about 2 km to the E of the KTB holes, capable of supplying sufficient neutron flux for considerable subsurface production of 36Cl. The Na–Cl–(K-, SO 4) precursor fluids of the Ca–Na–Cl brines were produced in the course of extensive tectonic processes since the Late Caledonian within the Bohemian Massif.

On the origin of saline fluids in the KTB (continental deep drilling project of Germany)

Highly saline fluids were encountered during the German Continental Deep Drilling Project (KTB) from depths ranging between 2 and 3 km to about 9 km. The most reliable data were obtained from samples extracted during a long-term pumping test in the 4000-m deep KTB pilot hole. Some 460 m 3 Ca Na Cl brines with about 68 g l −1 total dissolved solids (TDS) and some 270 m 3 associated gases, mainly N 2 and CH 4 were pumped to the surface from the main fracture system situated near the bottom of the pilot hole. Geochemical and isotopic data support the hydraulic tests which suggest the presence of an open and large fluid reservoir at depth. The pumped fluids from this main fracture system were released from a deep reservoir situated at more than 5500 m depth which is hydraulically connected with the 9101 m deep KTB main hole, drilled some 250 m to the northeast of the pilot hole. While Ca and Sr contents of the extracted brines may be the result of water-rock interaction, Cl is most likely of external origin. The Cl is hypothesized to derive from geotectonic processes rather than to descending infiltration of paleo-seawater (evaporitic brines). The sampled fluids have probably migrated from a deeper reservoir to their present position since the Cretaceous-Tertiary period due to tectonic activity. However, several isotopic studies have identified an admixture of descending paleowaters down to more than 4000 m depth. The high 36ClCl ratio of the fluids sampled during the long-term pumping test point to a host rock highly enriched in U Th, unlike the sampled KTB country rocks. The fluid reservoir is believed to be in contact with the Falkenberg granite massif situated about 2 km to the E of the KTB holes capable of supplying sufficient neutron flux for considerable subsurface production of 36C1. The Na Cl (K , SO 4) precursor fluids of the Ca Na CI brines were produced in the course of extensive tectonic processes since the Late Caledonian within the Bohemian Massif.

Evaluation of the Wear of the Pivot Bearing in the Gyro C1E3 Pump.

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 pump was estimated for various pumping conditions. The lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

Regional hydrodynamics of the proposed high-level nuclear-waste repository sites in the Texas Panhandle

Bedded salt in the Palo Duro Basin area of the Texas Panhandle is being evaluated as possible host rock for a high-level nuclear-waste repository. The two potential sites are underlain by three major hydrostratigraphic units: a shallow freshwater aquifer system developed in the Tertiary Ogallala Formation and the Triassic Dockum Group, a thick shale and evaporite aquitard developed in an Upper Permian evaporite sequence, and a deep-basin brine aquifer system predominantly developed in the Wolfcamp Series and the Pennsylvanian System. Water level, shut-in pressure, and specific-gravity data from inventoried wells, drill-stem tests, and long-term pumping tests were used to construct potentiometric surfaces, potentiometric profiles, and pressure-depth diagrams. Water in the Ogallala and Dockum aquifers predominantly flows horizontally and discharges to springs and wells. Equipotential patterns on potentiometric profiles indicate that some water may be moving downward from the Ogallala into the Dockum across an intervening confining unit, as well as moving downward from the Dockum across the shale and evaporite aquitard and into the deep-basin aquifer system. This is corroborated by the slope of pressure-depth data which indicate the potential for regional downflow in the shale and evaporite aquitard. Equipotential patterns and pressure-depth data indicate predominantly horizontal flow in the deep-basin aquifer system which is influenced by permeability variations related to facies changes. Hydraulic gradients are flatter in the more permeable shelf, shelf margin, and fan-delta facies and steeper in the less permeable deep-basin facies.

Unique Aspects of Drilling and Completing Hot, Dry Rock Geothermal Wells

Summary The drilling and completion of deep wells in hot, nonporous, crystalline basement rock has challenged conventional rotary and directional drilling tools, procedures, and instruments used for oil and gas drilling. Drilling operations at the Fenton Hill Hot Dry Rock (HDR) Geothermal Test Site have led to numerous developments needed to solve the unique problems caused by a very harsh downhole environment. The well site is on the western flank of a young silicic composite volcano in the Jemez Mountains of northern New Mexico. A pair of deep wells was drilled to approximately 15,000 ft [4.6 km]; formation temperatures were in excess of 600 deg. F [316 deg. C]. The wells were drilled directionally, and inclined at 35 deg., one above the other, in a direction orthogonal to the least principal stress field. The completion of this pair of wells is unique in reservoir development. The deeper well will be a cold water injector, cooled during injection from the static geothermal gradient to about 80 deg. F [270 deg. F. The upper well will be heated during production to more than 500 deg. F [260 deg.). The well pair is designed to perform as a closed-loop heatextraction system connected by hydraulic fractures, with a vertical spacing of 1,200 ft [366 m] between the wells. These conditions strongly constrained the drilling technique, casing design, cement formulation, and cementing operations. New and upgraded technologies have been developed to resolve the difficulties of completing these two wells. Introduction In natural, or hydrothermal, geothermal reservoirs, surface waters penetrate deep enough to contact hot rock. The fluids are heated by the rock but are trapped in a porous fractured system. A large circulating convection system of fluid has been established in places. Although these hydrothermal convection systems are rather rare, they are excellent sources of energy. The ratio of dry holes to production wells in hydrothermal exploration is highly variable, but averages about 3:1. Many of these dry holes are hot, having penetrated into a volume of hot rock that lacks fluid and natural permeability. Thus, dry but hot wells are excellent candidates for artificial stimulation, or for application of the HDR energy extraction concept. Project Description The production of heat energy from hot, dry rock entails creating fracture permeability at depth to permit circulation of water from the surface through wells. A preliminary project to develop this concept (Fig. l) was initiated by the Los Alamos Natl. Laboratory in 1972 and, in 1977–80, succeeded in producing the first two reservoirs in a hot, crystalline formation at 10,000 ft [3 km], where formation temperatures are 400 deg. F [204 deg. C]. Long-term pumping and temperature drawdown tests and reservoir simulations examined the technical feasibility of the concept for the commercial development of a larger and hotter HDR geothermal reservoir. These initial results prompted drilling a second pair of deep, 350-inclined wells, so that the development of a multiple, parallel fracture reservoir could be attempted. There were many unique problems encountered both in the drilling of these two deep wells into Precambrian crystalline rock and in the initial phases of the completion and hydraulic fracturing efforts. The drilling of the deeper well pair started with the spudding of Energy Extraction Well 2 (EE-2) on April 3, 1979. This injection well was drilled and cased in 409 days. The well was drilled directionally to a measured depth of 15,298 ft [4.7 km] and deviated in a direction orthogonal to the inferred in-situ least principal stress (Figs. 2A and 2B). The bottomhole static temperature (BHST) was recorded as 608 deg. F [320 deg. C]. The production well, Well EE-3, was directionally drilled so that the wellbore trajectory was spaced 1,200 ft 50 ft [366 m+ 15 m] directly above the injection well. Well EE-3 was speded May 22, 1980, and was finished 461 days later. Well EE-3 reached a measured depth of 14,933 ft [4.6 km] and a BHST of 580 deg. F [304 deg. C]. The EE-3 borehole trajectory was maintained vertically above Well EE-2 to an azimuth tolerance of + 100 ft [+30m]. This precision was required to maximize the chances for fracture connections during completion operations. Fracturing and completion operations were initiated April 4, 1982. These operations are still in progress (May 1985). JPT

Determination of transmissivity and storage of a large water table aquifer from long-term pumping test data

Determination of transmissivity and storage of a large water table aquifer from long-term pumping test data

Determination of Transmissivity and Storage of a Large Water Table Aquifer from Long-Term Pumping Test Data

The hydraulic characteristics of a large water table aquifer were investigated by performing a 60-day, 1,950 gpm pumping test. The test data were analyzed using the type-curve solution developed by Boulton (1963) and expanded upon by Prickett (1965). This solution considers the effects of delayed yield from storage common to water table aquifers. Corrections for decreases in transmissivity due to aquifer dewatering, recognition of the effects of nonradial flow, and checks using distance-drawdown methods permitted considerable editing and refining of the test data. Analyses of the results indicate that editing data from a water table test so that close agreement is obtained between the Boulton method and the distance-drawdown method is justified. The technique aids in identifying extraneous data and therefore enhances the accuracy of the resulting coefficients.

Hydrologic Characteristics and Response of Fractured Till and Clay Confining a Shallow Aquifer

Fractures in glacial till and glaciolacustrine clay were observed in excavations up to 20 ft (6.1 m) in depth and in drill cores at the Whiteshell Nuclear Research Establishment (WNRE) in southeastern Manitoba. The fractures are characteristically coated with carbonate and oxide precipitates, which indicate groundwater movement through the fractures. The fractures impart an effective bulk hydraulic conductivity to the clay–loam till and lacustrine clay, as evidenced by tritium tracer experiments and piezometer responses in the till and clay to pumping of an underlying sandy aquifer.The intergranular hydraulic conductivity of clay–loam till and glaciolacustrine clay in the Interior Plains, as determined from laboratory consolidation test data, is in the range of 2 × 10−10 to 9 × 10−11 ft s−1 (6 × 10−9 to 2.7 × 10−9 cm s−1). The bulk hydraulic conductivity of the fractured clay–loam till at WNRE, as determined from finite-element mathematical modeling, is about 6 × 10−9 ft s−1 (1.8 × 10−7 cm s−1). The model value represents the effective hydraulic conductivity imparted to the till by the fractures.Seven pumping tests, ranging in duration from 8.75 to 120 h were conducted on the sandy aquifer and drawdown data in the aquifer were analyzed to obtain the hydraulic conductivity and storativity of the aquifers.A 32 day pumping test on the aquifer showed that many of the piezometers in the till and clay respond quickly and strongly to the aquifer drawdown, while others show no noticeable response. The responding piezometers intersect open fractures whereas the others do not. Analysis of the piezometer drawdowns during the long-term pumping test using the Neuman and Witherspoon ‘ratio’ method indicates that the rapid piezometer drawdowns in the confining layers can be accounted for by assigning specific storativity values in the range of 1 × 10−5 to 5 × 10−6 ft−1 (3 × 10−5 to 1.5 × 10−5 m−1) to the clay–loam till and lacustrine clay. These values are typical of fractured rock. If intergranular specific storage values are used, the calculated piezometer drawdowns are very small or negligible.