# Presentation: 142718

## Utilization of a Regional Water Chemistry Database to Improve Formation Evaluation and Reservoir Simulation in Low Permeability Reservoirs of Southwest Wyoming

**DOE Contract DE-FC-02NT41437**
**Presented by:**
**Randal L. Billingsley**
**Maria W. Henry**
**Leta K. Smith**
**Keith J. Jagiello**
** **
**Advanced Resources International**
**April 28, 2005**
**AAPG Hedberg Conference**
**“****Understanding, Exploring and Developing Tight Gas Sands”**
**Vail, Colorado**

## Acknowledgements

**National Energy Technology Laboratory, Department of Energy, Funding through Contract DE-FC-02NT41437**
**Participating Parties**
**BP**
**Schlumberger**
**Bill Barrett Corp.**
**Anadarko**
**Devon**
**Shell**
**Stone**
**Ultra**
**USGS**

## Presentation Outline

**Database Overview**
**Field Study **
**Eastern Green River Basin**
**Conclusions**
**High Quality Water Chemistry has Improved Formation Evaluation in the Field Study Area**
**SP Used to Determine Gas-Water Boundary**
**Gas-water Boundary Usually Found Near Base of Significant Almond Coals (a local source for gas?)**
**Sands are a Series of Discontinuous Lenses**

## Database Overview

**Historical Data**
**3200 Well Locations/GGRB and WRB**
**8000 Chemical Analyses**
**Current Study**
**86 new samples with full analyses and isotopes**
**Waltman/Cave Gulch, Pinedale, Tablerock, Wamsutter**
**7 component “Stiff” Analyses**
**Strontium, Oxygen Isotopes**
**Highly Accessible**
**Quality Screened **
**Access/Excel Formats**

## Database Coverage

## Water Database Value

_**Catalogue of  Water Resistivity (RW)**_
_**Improved Formation Evaluation**_
_**Critical for delineating gas from fresh water **_
**Provide Source Point for Water Chemistry Ideas and Technology**
**Areas of Diagenetic Porosity Enhancement**
**Potential Flow Paths**
**Hydrologic Compartments**
**Basin Modeling Data**
**Database facilitates organization, mapping and analysis of large amounts of water chemistry data **

**Notes:**
Purpose to mitigate water production, which is a drag on economics.
Increase resource recovery, decrease water.

## Eastern Green River Basin Field Study

** **

**Wyoming**

**Colorado**

**Utah**

**Greater Green River Basin**

## Eastern Green River Basin Field Study

_**Operator Issue: How to minimize water while capturing additional resources?**_
**Long-lived historical production area**
**88 wells**
**40 BCF Cumulative Production**
**Water production problems**
**Available data**
**Well logs, core, 3D seismic, production data**
**Water chemistry data**
_**Technical Strategy: Improve formation evaluation, simulate reservoir to understand bulk permeability/water production**_**.**

## Stratigraphic ColumnWashakie Basin, Wyoming

- Modified from Roehler, 1990

**Almond**

- Mesaverde Group

- Ericson
- Formation

- Canyon Creek / Pine Ridge

**Upper Almond**

**Lower Almond**

- Campanian

- Maestrichtian

- Upper Cretaceous

- Lance Fm.

- Fox Hills Fm.

- Lewis Fm.

- Allen Ridge Formation

**Stratigraphic Column****Washakie Basin, Wyoming**

**Notes:**
Figure 2: Stratigraphic column for the Upper Cretaceous in the Washakie Basin area.

## Work Flow

**Build Stratigraphic Correlation Framework**
**Interpret 3D Seismic for Structure**
_**Perform Base Petrophysical Study for Reservoir Characterization**_
_**Emphasized Produced Water Chemistry for High Quality Formation Water Resistivity (Rw)**_
**Assembled 23 Unit Dual Permeability Reservoir Model**
**Discrete Fracture Network Permeability Grid**
**Constrained by Geomechanical Simulation of Basement Faulting**
**Matrix Porosity and Permeability From Petrophysics**
**Production History Match/Forward Simulation**

## Type Log

**Ericson**
**Coastal Plain/Fluvial**

## Water Resistivity (Rw) and Petrophysics

**Evaluated Regional Almond Rw Trends**
**Variable Rw influenced by Depositional Environments**
**9 Township Focused Area**
**Vertical and Horizontal Variation**
_**Established Rw-Total Dissolved Solids (TDS) Relationship**_
**Established Rw by Zones for Saturation Calculations**
- Aquifer water is so fresh (<5000 ppm NaCl) that it is difficult to distinguish from gas invaded by a fresh water filtrate
- Porous and permeable Ericson has high resistivity, although it only produces water
- Used water chemistry, fluids and logs in Upper and Middle Almond to calibrate Rw in gas zone, and the Ericson to calibrate Rw in the aquifer

## TDS/Rw Cross-Plot 68 degrees F9 Township Area

**TDS/Rw Cross-Plot 68 degrees F****9 Township Area**

**TDS**

- Rw

**Y=6264.6x^-0.9784**
**R^2=0.9788**

## AVERAGE PRODUCED WATER RESISTIVITY

- Red Shades indicate High Rw, Blue indicate Low  Rw (@ 68 F)

## SP-Rw

**SP-Rw**

**Medium salinity water in gas zone**

**Low salinity water in aquifer**

- Rw

- NaCl ppm

**SP Change **
**(Gas-Water Boundary**)

**Mungo Federal 1-14**

**Champlin 221C**

- SP

- GR

- SP

- GR

**Despite difficulties, SP to Rw calculations show a dramatic shift in formation water salinity in the upper (more saline) and lower (fresher) parts of the formation.****  **

**Notes:**
More Saline upper than lower
On right, curve showing NaCL calculated from SP 
More negative SP indicates fresher RMF than formation water
Despite difficulties, SP to Rw calculations show a dramatic shift in water salinity in the upper and lower parts of the formation. It is difficult to exactly calibrate Rw from the SP curve due to 
	Subjectivity in baseline shifting SP curve
	Variable amount of Bicarbonate in the water (700-2600 ppm)
Rw may be even more variable than water saturation model used in this study.
	Confirmed by variability in collected water analyses.

## Pickett Plot Gas Zone & Aquifer

**Pickett Plot Gas Zone & Aquifer**

**Water**
- Lower Almond & Ericson
- Vclay<10%
- a=1.0, n=2.00, m=1.74
- Rw=0.63 @ 200F
- NaCl=3,500 ppm

**Gas Zone**
- Upper & Middle Almond
- Vclay<10%
- a=1.0, n=2.00, m=1.74
- Rw=0.17 @ 200F
- NaCl=13,000 ppm

**Notes:**
Point out 100 percent water line and variable RW was used to constrain this
NaCL in Gas 13000 ppm versus 3500 ppm in water zone
Gas Pickett- most points between 25 and 60 percent
Water Picket – 60 and 100 percent SW

## Gas-Water Boundary & Coal & Wells

- Cathedral Federal 3-2

- Mungo Federal 1-14

- Wamsutter Rim 17-1

**GWB**

**GWB**

**GWB**

- SH2

- SH2

- SH2

- SH3

- SH3

- SH3

- Gas-Water Boundary is picked based on SP and/or Resistivity curves.
- Generally near Almd_SH2 and Almd_SH3 picks in this township.
- Usually appears near first significant appearance of coals, which is a presumed local gas source.
- Follows dipping structure, but not rigorously; therefore, is a boundary between discontinuous gas-charged
-     & aquifer sands rather than an actual contact.

**Notes:**
Gas-Water Boundary is picked based on SP and/or Resistivity curves.
Generally near Almd_SH2 and Almd_SH3 picks in this township.
Usually appears near first significant appearance of coals, which is a presumed local gas source.
Follows dipping structure, but not rigorously; therefore, is a boundary between discontinuous gas-charged 
    & aquifer sands rather than an actual contact.

## SP-GWC Structure Map

_**Gas-Water Boundary follows dipping structure, but not rigorously; therefore,  this is a boundary between discontinuous gas-charged & aquifer sands rather than an actual contact.**__  _

**Structure Map on Gas-Water Boundary**

**Structure Map on Top Almond**

## Testing Gas-Water Boundary Hypothesis

**The depth of the gas-water boundary was compared to the initial fluid production in 41 wells as reported in the Wyoming Oil and Gas Commission website.  **
**Initial Production tests above gas-water boundary (15 wells)**
**< 10 BWPD****	****	****17 tests**
**11-20 BWPD****	****	****  3 tests**
**21-30 BWPD****	****	****  2 tests**
**Initial Production tests below gas-water boundary (26 wells)**
**<25 BWPD****	****	**** 7  (4 not perf’d in permeable sand below GWB)**
**25-50 BWPD ****	****	**** 2 tests**
**>50 BWPD****	****	**** 20 tests**

## Conclusions

**High Quality Water Chemistry has Improved Formation Evaluation in the Field Study Area**
**SP used to determine gas-water boundary**
**Supported by initial production data (75% agreement)**
**Useful for perforation and completion strategy**
**Gas-water Boundary Usually Found Near Base of Significant Almond Coals (a local source for gas?)**
**Sands are a series of discontinuous lenses**