David P Dadzie

Master’s Student in Petroleum Engineering at University of Texas at Austin
Graduate Research Assistant – Bureau of Economic Geology

Research

Reservoir characterization – Inter-well connectivity project using the “Capacitance Resistance Model (CRM)” in the Katz Field.

Background

The Pennsylvanian (Desmoinesian) Strawn Formation along the eastern shelf of the Permian Basin is known to contain abundant oil/gas in both carbonate and siliciclastic reservoirs. The Katz Field found in northeast Stonewall County, TX is a siliciclastic-dominated play that also contains minor carbonate.  The Katz is a complex “facies mosaic” of sandstone, siltstone, mudstone, and crinoid-rich grainstone deposited within the extensive Haskell Delta System in the Pennsylvanian. Depositional environments include proximal to distal tidal deltaics and associated tidal shelf deposits  Permeability, the ability for fluid to flow between grains, changes rapidly over short distances. This geological complexity that can be broken down into manageable “layers” or zones” for fluid flow modelling purposes, combined with an extraordinary 70-year production history involving waterflooding and CO₂ injection, makes Katz a perfect natural laboratory for developing subsurface reservoir models. With a dense, closely spaced grid of over 150 wells the field also provides a relatively high-resolution data that is rarely available for Eastern Shelf oil/gas fields . My research leverages this unique dataset to test and refine the Capacitance Resistance Model (CRM), allowing us to map inter-well connectivity in heterogeneous siliciclastic systems where traditional models often struggle.

Overview

The Katz (Strawn) Field

The Katz (Strawn) Field represents a mature Texas reservoir with an extensive history of operations. The Katz (Strawn) Field was discovered in 1951, waterflood operations were initiated in 1984, and more recently shifted to CO2 EOR operations in 2010. This reservoir evolution has created an array of opportunities to observe reservoir behavior during different stages.

Geological Setting – Located in North Texas, the field has its source of production from the Pennsylvanian Strawn Formation, a complex geological system of multiple stacked sands from the Haskell Delta System, trending from the northeast. Complex field architecture is presented by three main zones of production, consists of sands at 4800′, 4900′, and 5100′, these zones are often commingled in production.

Research objectives

  • To characterize reservoir heterogeneity using CRM to analyze production and injection changes.
  • To integrate geological constraints with engineering signal processing (CRM).
  • To optimize future waterflood and Enhanced Oil Recovery (EOR/CO2) strategies based on zonal connectivity.

Why Integrate Geology?

Engineering data tells us where fluid is moving, while geology explains why. Relying on engineering data alone often yields “non-unique” solutions mathematically correct but physically impossible results.

By integrating geological constraints (e.g., faults, pinch outs) into the CRM workflow, we can eliminate unrealistic connections and derive a model that better represents the subsurface.

Methodology

Research workflow

Key Contributions

This research tackles the challenge of understanding fluid flow patterns in mature oil fields. By developing high speed analytical tools, we can identify which injection wells are connected to which production wells critical information for optimizing waterflood and EOR operations.

  1. High Speed Optimization Framework – Implemented the open-source Interior Point Optimizer (IPOPT) to reduce full-field connectivity analysis runtime by 98% (relative to SciPy’s optimizer).
  2. Interactive Visualization Platform – Built Python-based dashboards (Dash/Plotly) to interactively track well performance and connectivity, reducing data interpretation time for the engineering team.

Tools used in this study

What is the CRM?
  1. Interactive Well Performance Dashboard

Follow the link below to access the well dashboard

https://katz-field-dashboard.onrender.com (server loading time 1 minute)

Features,

  1. Interactive map with OpenStreetMap integration
  2. Click wells to instantly view performance history
  3. Multi-well selection for comparative analysis
  4. Combined rate charts for field-wide trends
  5. Date range filtering (1984-2010)
  6. Zone-based color coding (Multilayered reservoir)
  7. Real-time data visualization with Plotly

2. Connectivity Visualizer

The following link provides access to the visualization tool for interpreting interconnectivity results from the Capacitance-Resistance Model (CRM)

https://katz-connectivity-visualizer.onrender.com

Real world challenges – The Katz field

Applying this method to the Katz Field presented unique hurdles typical of mature assets

  • Data scarcity, Decades old completion and rate records were often vague, had errors or missing.
  • Commingled production, Production comes from three distinct stacked sands (4800′, 4900′, 5100′), making it difficult to isolate which zone is contributing to flow.
  • Operational noise, Distinguishing between true reservoir responses and operational fluctuations over a 20+ year history.