2.2 "Laboratory Measurements as the Ground Truth forShale Classification" - Greg Getz [EN]
1. South Baltic Gas Forum 2011 – Gdańsk, Poland Laboratory Measurements as the Ground Truth forShale Classification Greg Getz Business Development Manager - Continental Europe Reservoir Sampling and Analysis TerraTek Core Facility – Warszawa, Polska
11. Production managementCompletion quality The properties of source rock that make it amenable to producing hydrocarbons include fracture complexity and height growth, fracture conductivity, fracturing fluid compatibility, the ability to retain fracture surface area during production, and pressure management during production.
27. Reservoir Quality - Absorbed Gas, Interstitial Gas, and Total Gas Content Total gas Interstitial gas Adsorbed gas The pressure dependence for storing interstitial gas in pores and adsorbed gas in organic surfaces is markedly different.
29. Reservoir Quality – Tight Rock Analysis (TRA) taken from biscuit (2/3 section) Sample Analysis Core Description TRA Porosity Perm Saturation 2/3 Slab 1/3 Slab Section for TS, SEM, XRD and TOC SEM TS TOC XRD 14
30. Heterogeneity —“Scratch Testing” Fine-scale heterogeneity is obtained via continuous measurements of unconfined strength along the length of the core. Results provide a profile of rock unconfined compressive strength and its mechanical variability.
39. Reservoir Quality – Unconventional MicroScale Mineral framework Conventional Sandstone Gas shale Kerogen Pore system 700 mm 100 mm Free gas in pore space Free gas in pore space Adsorbed gas on kerogen
44. Reservoir Quality – Shale Gas Core/Log Evaluation RHOB RHOM TOCPerm GIPGas-Phi SwPorosity GR Resistivity ECS / XRD Porosity ELAN
45. Log-Scale Heterogeneity Obtained Through Heterogeneous Rock Analysis (HRA) Log-derived facies …that can be populated with core-measured properties. Each facies represents a container… Log data, e.g., Platform Express* data ECS*/ELAN data Sonic Scanner* data Core data Reservoir quality data Mechanical data Fluid Sensitivity data Petrology Calibrations
64. Completion Quality – Strength and Elastic Anisotropy Testing vessel and sample stack Poisson’s Ratio Triaxial Compression Strength Young’s Modulus
65. Completion Quality - Proppant Embedment/Fracture Conductivity Evaluate fracture conductivity loss as a function of pressure depletion due to proppant embedment or crushing. Rock softening as a result of rock-fluid interaction might induce this behavior. Goal: Optimize proppant size and concentration. Fracture conductivity, md-ft Closure stress, psi
66. Completion Quality – Design Application Determine in situ stress contrast. Anisotropy can change this significantly. Supporting measurements: Heterogeneous rock log analysis Anisotropic elastic properties Reservoir pressure Field stress measurements (MDT* modular formation dynamics tester) Fracture conductivity/proppant embedment Modeling provides an estimate of expected fracture geometry
68. Integration of Reservoir Quality and Completion Quality Good RQ + Good CQ = Good well Good RQ + Bad CQ = Bad well Bad RQ + Good CQ = Bad well Bad RQ + Bad CQ = Bad well Contour map of Reservoir Quality Contour map of Completion Quality
69. Mapping RQ And CQ Sweet Spots Region with high RQ and good CQ. These are easy targets. Regions with high RQ and poor CQ. These are engineering challenges. Region with poor RQ and bad CQ. There is no potential (hopeless case).
72. Completion Quality – Baltic Basin Completion Quality ??? Well A Closure variability 0.15 psi/meter - Good Clay Volume < 25% - Good No ductile clay - Good Well B Closure variability - ? Clay Volume > 50% - Poor Some ductile clay – Poor
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74. Given the low total porosity (< 10%, Track 1) dynamic moduli compare better with laboratory measurements (Track 3)
75. Poisson’s ratios should be refined (Track 4), although lab measurements and model predictions are in good agreement in the isotropic sections (see ~ 1000 m MD)
76. Predicted anisotropic FG at perforation depths using static moduli from sonic logs and tectonics (Ex=0.3 Ey=0.8) are (Track 6) 0.65 psi/ft @ 1000 m MD 0.85 psi/ft @ 1500 m MD
77. Building Regional Models Extending to seismic volume Mapping reservoir potential Basinwide heterogeneous rock analysis model
78. Natural Gas for Europe http://naturalgasforeurope.comMonday, September 05, 2011 “BNK Updates on Saponis Baltic Basin Shales” …The TOCs in the Lebork S-1 well ranged from 0.14 to 1.50, averaging 0.8 by percent weight for the Lower Silurian, 0.04 to 6.04, averaging 2.2 by percent weight for the Ordovician and 5.0 to 9.2, averaging 7.2 by percent weight for the Cambrian. Also received were the Porosity values of the 148 meter thick Lower Silurian interval which ranged from 1.0 to 9.6, averaging 3.9% in the Lebork S-1 well… BNK also announced that the Starogard S-1 …There were 107 meters of whole core recovered from the well and a full suite of logs was run. In addition, 100 sidewall cores were taken above the whole cored interval where good gas shows and preliminary log analysis indicate potential.
79. Reservoir Heterogeneity can be measured and scaled up Reservoir Quality can be quantified and mapped Completion Quality can be quantified and mapped “Ground Truth” core data provides a reliable foundation for determination of unconventional shale Reservoir Quality and Completion Quality An integrated workflow is required to characterize shale reservoirs Higher understanding means less risk and more productivity Conclusions
Tight Rock Analysis (TRA) is a TerraTek workflow designed to address the Heterogeneic nature of unconventional resources. You could refer to Heterogeneity as “Elephant #1.”
From this diagram we can clearly see some of the resolution challenges that seismic faces when compared to other sampling techniques such as logging and core samplingIt becomes clear that seismic cannot go it alone when exploring the heterogeneous nature of this rock (next slide)
As you scan your eye across these shale gas logs taken from key shale plays you can seen how some have more calcite while others have more claysYou can also see how they change vertically Note the vertical Heterogeneity with in all these reservoirs
The Slide on the left shows the pore structure of a conventional sandstone and we can clearly see the pore structure and mineral frameworkHowever, in when we look at shales under the microscope we have to zoom in much closer to see any type of pore structure, the slide on the RHS has been overlaid onto the slide on the LHS at the same scale to demonstrate the difference in this rock fabricThe pore structure we are used to seeing in the sandstones are lost in the shales and replaced by fossil fragments, kerogen, minerals and clays We cannot simply apply sandstone technology to Shale they are very different and need to be managed differently.
Understanding how the rock fabric effects the completion quality is also an essential part of the puzzle Measuring the mechanical properties of the shales in the lab and the field is essential to building this understandingThe variation seen from play to play and even within a few hundred yard can have a dramatic impact on the completion qualityIf stress barriers are not located fractures can easily grow out of zone If we find high stress anisotropy this may produce a completely different result from rock with lower stress contrastIt is not enough to only look at the reservoir quality we cannot expect good results without also evaluating the rock mechanics and completion qualityAt the end of the day it is the rock that matters
