The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
- Data Science & Engineering Analytics
The SPE has split the former "Management & Information" technical discipline into two new technical discplines:
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Nuszkowski, J. (School of Engineering, University of North Florida) | Thomas, A. (School of Engineering, University of North Florida) | Hudyma, N. (School of Engineering, University of North Florida) | Harris, A. (School of Engineering, University of North Florida)
Abstract: Understanding thermal properties is necessary for the development of both shallow and deep geothermal systems. Thermal properties can also be used for understanding the development and assessing weathering in a variety of materials. An experimental apparatus has been developed to determine the thermal properties of rock samples. The apparatus consists of a ring heater, aluminum adaptor, and a stainless steel base. Three thermocouples are used to measure heat flow through the base. The rock specimen sits on top of the stainless steel base. Twelve thermocouples, arranged vertically in sets of three at the cardinal positions around the rock sample, are used to measure heat flow through the sample. The apparatus is wrapped in insulation to prevent heat loss. The top of the apparatus is open so a thermal camera can capture the temperature increase at the top of the specimen. Thermal analyses conducted using finite element modeling have verified the design of the apparatus. Two limestone specimens have been tested and experimentally derived thermal conductivities are within experimental ranges of thermal conductivities presented in the literature. Introduction Understanding the thermal properties (thermal conductivity, thermal diffusivity, and heat capacity) of rock is important for regional geothermal and ground source heat pump applications. Ouali (2009) studied the variation in thermal conductivity of a stratigraphic column with varying porosity in Reykjavik, Iceland. Goto and Matsubayashi (2009) investigated the correlation of thermal properties in the Juan de Fuca Ridge as a function of porosity and depth. Additionally thermal properties may provide insight into the weathering state of specimens. Banks et al. (2010) studied the use of thermography for structural health monitoring of subsurface anomalies in porous materials. The thermal properties of rock can be estimated based on the rock porosity with varying accuracy.
This paper was prepared for, but not presented at the SPWLA 57th Annual Logging Symposium held in Reykjavik, Iceland June 25–29, 2016. Abstract Hydraulic fracturing is established as the technology for economic exploitation of tight reservoirs. The inherent natural fractures (NF) in the rock fabric provide enhanced porosity and permeability, whereas induced hydraulic fractures (HF) provide pathways for hydrocarbon flow into the wellbore. Understanding hydraulic fracture mechanism and its interaction with natural fractures plays a vital role in assessment of stimulated rock volume (SRV) and prediction of flow rates. Barmer Hill formation in Mangala & Aishwariya area of Barmer Basin (North West India) is a low permeability laminated Diatomite/Porcellanite reservoir with high porosity (20–35%) but low matrix permeability (0.2-4mD). Conventional cores, image logs, and well test data suggest presence of natural fractures in this reservoir. After the initial success of production testing with HF in appraisal/development wells, it was felt necessary to understand the NF-HF interaction in these reservoirs for large scale field development. Understanding of rock failure mechanism and geomechanical properties (Young's Modulus, Poisson's Ratio and Uniaxial Compressive Strength) are important in designing a frac job. However, well flow rates are very much dependent on the rock fabric and natural fracture characteristics. Hence better understanding of interaction of hydraulic fractures with natural fractures is essential for successful field development. To understand NF-HF interaction, an innovative idea was tested using time lapse image log acquisition plan during multiple phases of induced hydraulic fracture operation. Generally, oil-base mud is used for drilling in this area to avoid shale stability problems; however, Well-X was drilled with water base mud in Aishwariya Field to obtain high-resolution micro-resistivity imaging. A pre-frac "base" Image log (Run-1) was acquired to identify laminations and presence of natural fractures & their orientation. Consecutively induced hydraulic fracture was initiated using water and then by proppant separately in two operations. Image logs were acquired after each operation as Run-2 (post step rate test-1) and Run-3 (post step rate test-2). Base image log indicated variations in angle and distribution of natural fractures in different units of Barmer Hill. Comparison of subsequent image logs brought out that while the rock was relatively resistant when homogeneous on image logs, the laminations helped in hydraulic fracture initiation. Presence of pre-existing fractures at high angle (>30deg) helped in fracture initiation while no hydraulic fractures could be generated where low angle fractures (<15 deg) existed. This is in agreement with the principle of critically stressed fractures. It was also evident that new induced fractures were created using water & proppant and also further accentuated the natural fractures. Micro-seismic monitoring in key wells in the Barmer Hill also confirmed that the rock develops tensile failure along maximum horizontal stress direction in this low anisotropy environment along with frac continuity between the layers. This innovative field experiment was also useful to understand the rock behavior at micro & mega-scale. This innovative data acquisition program is "first in type" and can act as a benchmark study to understand the natural/hydraulic fracture interaction in fractured reservoirs.
This paper was prepared for, but not presented at the SPWLA 57th Annual Logging Symposium held in Reykjavik, Iceland June 25–29, 2016. Abstract Naturally occurring fractures often play a very critical role in defining a shale play, and fracture identification, typically from image logs, has become a key component in a range of situations from efficient drilling design to reservoir development. In this vein, to complement the usage of image logs in fracture detection work, recent applications of multi-component (or triaxial) induction log data were investigated in a four-well US resource play case study. The multi-component induction tool data was acquired in all four vertical wells in the study. All of these were drilled with oil base mud systems. Additionally, electrical and acoustic imaging logs were run in three of the wells to corroborate the fracture indications between the various tools. Whole core was also available to provide visual physical evidence of fracture existence and features. Inversion of multi-component induction data normally yields bedding dip magnitudes and azimuths. An extension of this inversion technique also now provides a qualitative indicator of high-angle fracture presence and intensity from the same data. It is also noted that these fracture planes do not have to intersect the borehole, but can be several feet away and still be detected. The focus of this work was to benchmark induction tool-based fracture characterization in oil-based mud against both slabbed core and traditional wellbore imaging log interpretation. In one of the wells where operational problems precluded image log acquisition, only the induction data was finally available. In this case, we found an important correlation between the induction log fractures derivation and drilling events and data. We assert that this new process promises to be an important tool for the recognition and characterization of natural fractures, especially in conditions where pad-contact image logging tools are sensitive to washouts, rugose borehole, deviated wellbores and other adverse borehole conditions, and especially in heavy oil-based mud where acoustic and electrical data quality is often compromised.
ABSTRACT Low-temperature geothermal water in Iceland generally has high pH, low conductivity, and is oxygen free, resulting in negligible corrosion. However, with ingress of oxygen, due to contamination of fresh water as an example, the corrosion rate can increase significantly. In order to establish methods of monitoring corrosion under these conditions, several corrosion monitoring methods were tested in two locations in Reykjavik, Iceland and one location in Keflavik, Iceland. It was found that electrochemical tests tended to overestimate the corrosion rate due to the slow polarization behavior of the system, while weight loss techniques required too long of an exposure to provide real-time information; although they gave reliable historical data on the corrosion that had accumulated over the previous three, six or twelve months’ time. A differential ER-probe proved to be the most promising measurement technique for these conditions. The analysis of the corrosion products using EDS and XRD further disproved the common notion that the low corrosion rate found in the geothermal water was due to the formation of a protective iron sulfide film. No iron sulfide film was detected, but with the ingress of oxygen, a thick magnetite film was detected. The low corrosion rate is therefore due to the favorable water chemistry, which leaves the carbon steel pipe surface vulnerable to corrosion if it is exposed to an oxidant.
ABSTRACT ABSTRACT: We report on two sites in Iceland, Blanda and Kárahnjúkar, where hydraulic fracturing stress measurements were performed in the initial stages of pre-excavation design of two underground hydroelectric projects. The dominant rock is young basalt, naturally fractured and blocky. The measured stresses were used in both cases to define the boundary conditions in the modeling of the stability conditions around the powerhouse caverns. Both caverns have been successfully constructed. 1 INTRODUCTION The advent of the hydraulic fracturing (HF) method of deep in situ stress measurements some 35 years ago has been of particular importance to the hydroelectric power (HEP) industry. Until then the state of stress at the site and depth of the major underground components of a planned project was typically unknown in advance of excavation. In the absence of that unique parameter the design of cavern stability, orientation, and support, among others, had to be mostly guessed until excavation, at which time any needed corrections would be very expensive. The ability to use HF at any depth that a borehole could reach enabled the measurement of in situ stress early in the site investigation stage, and thus provided crucial information for the pre-excavation design of the underground works. The first projects that took advantage of the new stress determination technique were the Helms and Bad Creek hydroelectric schemes in California and South Carolina, respectively (Haimson 1977). Since then, the use of HF ahead of excavation has become routine all over the world. In Iceland, starting in the late 1970’s, HF stress measurements were conducted at several potential hydroelectric sites. This paper reports on two case histories, Blanda and Kárahnjúkar, where HEP projects were constructed. The Blanda Hydroelectric Project is located in northern Iceland, some 340 km from the capital city of Reykjavik (Fig. 1).
ABSTRACT ABSTRACT A recently-drilled ultra deep oil-well near the center of the Michigan Basin has provided an excellent opportunity to determine the state of stress and its variation with depth in formations ranging in age from Precambrian to Devonian. Except for the top test (1230m deep), results in the other three horizons (2806m, 3660m, 5110m) indicate a linear increase of sHmin yielding a constant ratio of 0.7 between sHmin and sV. The shallowest test in the Devonian Amherstburg Formation yielded a sHmin approximately equal to sV. Shallow measurements elsewhere in the Midwest have shown similar trends of relatively high horizontal stresses. The value of sHmax while not too consistent, tends to be equal or lower than sV at the three deepest levels tested. Hydrofracturing stress measurements have been carried out to about 0.4 km in two boreholes in Reykjavik, Iceland, on the flank of the Mid-Atlantic Ridge. The measurements indicate a dominant orientation of sHmax approximately perpendicular to the axial rift zone, in contrast to earthquake focal mechanism solutions from within the axial rift zone. In one hole (H32) a depth-dependent change in stress orientation is indicated, with the maximum compressive stress horizontal above a depth of about 0.25 km, and vertical below it; however the orientation of sHmax remains unchanged. The data thus suggest reconciliation of an apparent conflict between the dominantly compressive indications of shallow overcoring stress measurements and dominant extension as required by focal mechanisms solutions. The measured stresses are supported by the more reliable of overcoring measurements from southeast Iceland. INTRODUCTION Hydrofracturing as a method of n-u stress measurement was developed a decade ago based on theoretical work (Scheidegger, 1962; Kehle 1964; Haimson and Fairhurst, 1967), and laboratory experiments (Haimson, 1968; Von Schonfeldt, 1970). Additional theoretical and laboratory studies have been carried out during the present decade (Edl, 1973; Haimson and Avasthi 1.975; Roegiers, 1975). Initial field results based on oil-field hydrofracturing jobs (Scheidegger,-1962; Kehle, 1964; Haimson and Stahl, 1970), and small scale experiments (Von Schonfeldt, 1970) were very promising. The opportunity to test the method as a field stress measuring technique came at Rangely, Colorado. The nu stresses as determined by Haimson(1973) using the hydrofracturing technique in a 1900m deep borehole were in according with the nearby fault type and its slip direction as well as with surface stress measurements and other geological structures. More importantly, the determined stress magnitudes together with the slip criterion of the rock tested were used to accurately predict the level of formation pore pressure that would induce slip, thereby triggering local earthquakes (Raleigh et al, 1976). Since the Rangely tests hydrofracturing has become a familiar nu stress measuring method and it is still to date the only technique known for depths larger than 50m. Some twenty significant measurements have been carried out so far in the North American Plate (e.g. Haimson, 1974a, 1975, 1976a; Haimson et al 1976; Zoback et al, 1977). In this paper I am reporting on two sets of hydrofracturing measurements recently conducted in areas of particular geologic interest: the Michigan Basin and the Mid-Atlantic Ridge in Iceland.