This document summarizes a conference on tight shales held in Warsaw, Poland in March 2011. It discusses how tight shales are not all the same and differ in their reservoir quality. Methods for characterizing and analyzing shale such as micro-structure observations, core analysis, well logs, and hydraulic fracturing are presented. The heterogeneity and natural fractures within shales are shown to create complex hydraulic fractures. Different conceptual fracture models are evaluated using reservoir simulation to demonstrate how fracture geometry impacts production outcomes. While knowledge is advancing, the document concludes that understanding the rock properties remains important for improving shale reservoir performance and lowering technical risk.
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2.1 "Tight Shales - Not all Shales are Created Equal" - Sidney Green [EN]
1. South Baltic Gas Forum Gdansk, Poland 5-8 Sept. 2011 Tight Shales-Not all Shales are Created Equal Sidney Green University of Utah / Schlumberger Innovation Center
2. Improving reservoir performance, lowering technical risk Tight Shale Conference March 2011 Warsaw Poland Organizers: Sidney Green Roberto Suarez-Rivera / Innovation Center Raymond Levey / EGI Univ. of Utah Wieslaw Prugar / Orlen Upstream Focus: On the “rock” following the belief that “Rocks Matter” Goal: To develop a better mental picture of tight shales Overall Conference: Poland was a great host and provided a great setting for the Conference Improving reservoir performance, lowering technical risk Improving reservoir performance, lowering technical risk Improving reservoir performance, lowering technical risk Improving reservoir performance, lowering technical risk Improving reservoir performance, lowering technical risk
7. Improving reservoir performance, lowering technical risk Changes in the Energy ‘Picture’ In the past year, major changes have occurred: The GOM oil spill changed offshore drilling greatly in the US The Japan earthquake changed the perception of nuclear energy worldwide US Shale gas has changed from an unqualified hero to an environmental concern The “Arab Spring” has led to disruptions and uncertainties regarding world oil production These are big, big changes -----
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9. How do we tell high Reservoir Quality from poor Reservoir Quality ?
10. Tight Oil and Gas Shale Core Improving reservoir performance, lowering technical risk
14. Improving reservoir performance, lowering technical risk Core Analysis Diamond Scratcher Continuous Profile Scratch Test Rock Core
15. Improving reservoir performance, lowering technical risk Well Logs Typically the Vertical Pilot Well is Logged with only Limited Logs taken in the Horizontal Borehole
21. Improving reservoir performance, lowering technical risk The Heterogeneous Nature of Shales cannot be Ignored Heterogeneous Formation Complex Hydraulic Fractures
22. Improving reservoir performance, lowering technical risk Rock Hydraulic Fracture Hollow whole-core cylinder specimens subjected to uniform external confinement and internal borehole pressure. The rock fabric determines the fracture initiation and the orientation of fracture propagation.
29. Improving reservoir performance, lowering technical risk Wellbore Mechanics(Breakdown Stress) Argillaceous Argillaceous Siliceous Siliceous The breakdown pressure is related to far field stresses through the anisotropic elastic properties
30. Improving reservoir performance, lowering technical risk Conceptual and Eclipse Fracture Models Conceptual Models for Different Fracture Geometries Yellow is Primary Fracture and Black is Secondary Fracture System Eclipse Models Used to Model each Conceptual Model Vertical Wellbore “Base Case” (not shown) is Primary Fracture only, with no conductivity for Secondary Fracture System Horizontal Wellbore Case 2 Case 4 Case 1 Case 3
31. Improving reservoir performance, lowering technical risk Daily Productions from 10 Days to Six Months Initial Production and Early Time (Time Zero Estimated) Case 2 1 & 2 Case 4 4 (green) Base Case Case 3 3 Case 1 Base Case
32. Improving reservoir performance, lowering technical risk Cumulative Productions Case 3 56 % increase over Base Case All ~35 % increase over Base Case Case 2 Case 4 Different geometries lead to different cumulative productions Case 1 Base Case
So, we are now aware of a number of geochemical and material aspects of the rockChemomechanical failureWater retentionSalt production and chemical scale formationAs with other petrophysical and mechanical properties we also know that these properties are heterogeneously distributed through the formation – nice to know.But what do we do with the information – how do we act on it? How do we convert reservoir knowledge to production wisdom.In the last few minutes I would like to discuss two very practical uses for this information. First – is the issue of fluids, proppants and additives – As you consider field development – materials costs are one of the biggest single ticket item in the cost of developing a field . How do you make rational choices with regards to these decisions?Although fluid sensitivities can vary over a matter of inches to feet, the fracturing treatments designed for these formations will be in contact with hundred’s of vertical feet in the reservoir, and over 1000’s of latteral feet – so what is the best fluid?David Handwerger and Roberto introduced the concept of HRA yesterday – and we are applying it to fluid sensitivities.Sample SelectionAdditive EffectivenessMeaningful criteria for overall fluid selectionEconomics are critical – due to the large volumes of fluids and proppant required – are you getting the value for them?
