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Abstract A study was initiated to improve the geomechanical input to the full field compaction/subsidence prediction model for Valhall and wellbore stability analysis models used to plan long extended reach wells in the Valhall field. The results are also applicable for other geomechanical activities in the field, like well design, waste injection, hydraulic fracturing stimulation in the reservoir and the design of a potential waterflood. The study used an integrated approach to characterize the Tertiary formations above the chalk reservoirs. In-situ stresses (magnitude and direction), pore pressure and geomechanical deformation properties of the formations were determined. Results, observations and conclusions are presented. P. 193
- North America > United States (1.00)
- Europe > Denmark (0.94)
- Europe > Norway > North Sea > Central North Sea (0.67)
- Phanerozoic > Cenozoic > Tertiary (1.00)
- Phanerozoic > Cenozoic > Paleogene (0.70)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.71)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.49)
- South America > Colombia > Llanos Basin (0.99)
- Europe > United Kingdom > North Sea > North Sea Basin (0.99)
- Europe > Norway > North Sea > North Sea Basin (0.99)
- (17 more...)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Integration of geomechanics in models (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Prediction of Rock Parameters from Micro-Indentation Measurements: The Effect of Sample Size
Ringstad, Cathrine (IKU Retroleum Research) | Lofthus, Ellen Benedikte (NTNU) | Sonstebo, Eyvind F. (IKU Petroleum Research) | Fjaer, Erling (IKU Petroleum Research) | Zausa, Fabrizio (ENI Spa - AGIP E&P Divison and Giin-Fa Fuh, Conoco Inc.) | Fuh, Giin-Fa (Conoco, Inc.)
Abstract Micro-indentation measurements have been performed in order to investigate the possibility of extracting rock mechanical properties from small rock samples. The tests were performed with a 1 mm flat indenter. Two parameters were determined when analyzing the indentation measurements: The Indentation Modulus (IM) and the Critical Transition Force (CTF). IM is the slope of the force-displacement curve, corrected for deformations in the load frame. CTF is defined as the force level where the material deforms without significant change in the applied force. The rock samples were casted in a mounting material (Demotec 30), in order to stabilize the sample during testing, and simplify surface preparation. The upper and lower surfaces of the samples were made flat and plane parallel by grinding. 15 materials were tested, including sandstones, limestones and shale/clay materials with different strengths and stiffness. The micro-indentation measurements showed that both IM and CTF were significantly affected when the experiments were performed on small samples with volumes ranging from 0.04 Cm3 to 0.7 cm3. Correlations combining the Uniaxial Compressive Strength (UCS), Young's Modulus (E) and porosity () with IM and CTF have been made. For measurements performed on small rock samples (embedded in Demotec 30) the following correlation with Uniaxial Compressive Strength was found: UCS = 0.149 CTFR2=0.90 The correlation is only valid for small samples embedded in a mounting material with the same indentation properties as Demotec 30. It is not recommended to use the micro- indentation measurements to predict porosity and Young's Modulus. P. 487
- North America > United States (0.30)
- Europe > Norway (0.28)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.59)
Abstract This paper gives effective procedures to drill wells in a depleted reservoir. From the fact that depletion result in decreased horizontal stresses and fracture gradients, the working hypotheses is that a depleted reservoir should be drilled by keeping the Equivalent Circulating Density (ECD) as low as possible. This have been achieved by using a low mudweight and applying the downhole pressure sub actively; which imply focus on the combination of hole cleaning, lower pump rates, avoiding backreaming, and careful breaking of circulation before pumps are started. The pressure sub and theoretical calculations show that bottom hole pressure give peak values under the following circumstances: Too quick start of pumps/breaking circulation, too high mudweight, too high mud viscosity, too high tripping velocity, poor hole cleaning, too high pump rates, and pressure pulses. Other factors which may have some influence on the bottom hole pressure are: Well stability problems leading to excess fill and loading of the well, and unstable mud. An additional method to reduce the ECD is to increase the fluid column diameter by installing liner instead of casing or by drilling holes with a larger diameter. Also, an exact calculation of the ECD is useful. Three cases from three different wells are discussed, and theoretical calculations and observations are compared. We also observed that the fracture gradient of the borehole wall increased with time, which is useful if it is not possible to go below the minimum fracturation gradient. P. 77
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Fault > Dip-Slip Fault (0.46)
- Europe > United Kingdom > North Sea > East Shetland Basin (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Statfjord Group (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Lunde Formation (0.99)
- (31 more...)
Abstract The rock mechanical behaviour of reservoir rocks is important in the design and implementation of drilling and production programmes. Traditionally rock mechanical properties are obtained from direct measurement on core samples or from mechanical calculations on acoustic wireline log measurements. This paper reports the rock mechanical properties of many different reservoir rocks of different porosities. This has led to the development of a new method of predicting rock mechanical properties directly from porosity. The paper discusses the measurement of experimentally derived porosity, elastic moduli and fracture strength parameters and the intetpretation of these mechanical properties results into direct correlations with porosity. The application of these results to obtain continuous rock mechanical property plots of the reservoir from wireline derived porosity is discussed. The practical use of these rock mechanical property profiles in drilling, production and enhanced reservoir simulation is also emphasised. Porosity (), modulus of elasticity (E), Poisson's Ratio (v), uniaxial compressive strength (UCS), cohesion (), angle of internal friction (), and triaxial stress factor (k), were measured on samples from a wide range of North Sea reservoirs using a conventional triaxial testing machine. This paper describes the procedure used and presents the correlations obtained from plotting each of the rock mechanical properties against porosity. The derivation of wireline porosities along with empirical corrections are presented and the results of applying the correlations to these wireline derived porosities to produce continuous rock mechanical property plots are discussed. Logs were calibrated to core-measured values to reveal realistic elastic and inelastic moduli profiles. The continuous property logs provide a reasonable estimate of the possible behaviour at discrete points throughout the reservoir interval, but they are limited in their description of the behaviour of individual beds as coherent bodies. A technique has been developed to pick out these individual beds and assess how they will perform as Rock Mechanical Coherent Units, i.e. sets of beds that perform in a similar or dissimilar manner to adjacent layers. Finally a discussion on how the results are used to aid production and generate enhanced reservoir simulation will be presented. P. 169
- Europe > United Kingdom > North Sea (0.26)
- Europe > Norway > North Sea (0.26)
- Europe > North Sea (0.26)
- (2 more...)
- Research Report (0.54)
- Overview (0.54)
- Well Drilling > Wellbore Design > Wellbore integrity (1.00)
- Well Drilling > Wellbore Design > Rock properties (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Abstract In 1993, during the development of the European hot-dry-rock geothermal field at Soultz-sous-Forets (France), 44,000 m3 of water were injected to stimulate the natural fracture system of this granitic rock mass. Some 16,000 microseismic events were recorded by a network consisting of a hydrophone and three four-component seismic sensors cemented in the granite at the bottom of observation wells. Multiplets (close earthquakes with similar waveforms) are retrieved in order to find local structures and correlate them with major fractures observed in the well by acoustic imaging and flow logs. Among the eleven identified and relocated multiplets, eight of them deline a planar structure, which is presumed to be a fracture plane. Two of the multiplets lie on a linear structure and one of them is the intersection of two previous planar multiplets. This leads to a description of the fracture network within a few tens of meters around the borehole. In addition, in order to compare the geometrical rupture parameters of the "multiplet" fractures with those of the "borehole" fractures, focal mechanisms of multiplets are modeled by using a statistical approach. This is done by combining the geometry of the fracture planes, the P wave polarity and the S wave polarization, as seen only at the four stations. The S waves polarization shows an hexagonal anisotropy with a North- South horizontal symmetry axis, which is consistent with the regional maximum horizontal stress direction. P. 545
- North America > United States (1.00)
- Europe > France > Grand Est > Bas-Rhin > Soultz-sous-Forêts (0.25)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.88)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource > Hot Dry Rock (0.34)