Presentation on theme: "Unconventional Petrophysical Analysis in Unconventional Reservoirs"— Presentation transcript:
1 Unconventional Petrophysical Analysis in Unconventional Reservoirs Putting the Puzzle Together in Gas ShalesLee Utley
2 “Intuitively, it is my belief that this magnitude of money could be better spent on other projects.” Executive with Mitchell Energy in his recommendation for attempting the first completion in the Barnett Shale ‘discovery’ well (Slay #1)
3 “Why are we spending all this money to find out how much gas is in the Barnett? If we really want to know what will happen in Johnson County, we just need to drill some damn wells!Engineering executive with Mitchell Energy upon finding out the magnitude of our planned spending on coring and analysis to reevaluate the gas content of the Barnett
5 Has this happened to you? Somebody just dumped some stuff in your officeLarge stack of logsSeveral CDs/DVDs of digital dataCore reportsSeveral maps and cross-sectionsYou are told that your company wants to get into this Barnett Shale play everyone is talking about so you need to figure this out.
7 General Goals Evaluate the resource Areal extent Thickness Type of hydrocarbonPossible production mechanismsBarriers to economic productionEvaluate the resource
8 Specific Goals to Achieve Using Log Analysis Gas ContentAnalysis of ‘conventional’ formationsMaturityTotal Organic ContentPorosityWater saturationLithologyRock PropertiesFracture types
9 Why is this so hard to do? Old logs with limited information Little or no core dataComplex lithologies cause problems with typical methodsTOC calculation is difficult at bestPorosity determination is complicated by presence of TOC
10 Useful Core Data Geochemical analysis (Ro, TOC, etc…) Porosity Water saturationGas content (including adsorption isotherm information)Mechanical properties
12 Gas Storage Sites Sorption – TOC Pore space Open natural fractures Most gas is stored in the pore space and the TOC. Fracture storage is usually minimal and probably can’t be quantified.
13 Calculation of Gas Content For sorption, relate TOC to gas content – usually through Langmuir parameters.Don’t forget about non-methane adsorptionFor pore space, use conventional gas-in-place equations.TOC and porosity are two of the biggest keys in looking at gas shales.
24 Standard Porosity Transform Core matrix numbers exclude organic material.Normal log presentations show very high apparent porosities. These porosities are closer to the volume of pore space and organic material combined.
25 Basic Porosity Equation Rock contributionFluid contribution
26 Porosity Equation with TOC Rock contributionFluid contributionTOC contribution
37 Use Lithology to Correlate with Rock Properties Neural Network of Young’s Modulus in Two Permian Basin wells using a Fort Worth Basin ModelRock Properties Computed Young’s ModulusNeural Network Computed Young’s Modulus
48 Gas shales can be effectively analyzed Maturity, TOC, and porosity are some of the keys to gas shale analysis and can be determined from logs.Even without extensive core data, gas shales can still be analyzed, at least in a relative sense.Other gas shales can be evaluated from log data and core data using these techniques. An integrated study is required for full evaluation.
49 Unconventional Petrophysical Analysis in Unconventional Reservoirs Putting the Puzzle Together in Gas ShalesLee Utley