This is the second of a three-part tutorial describing a workflow for evaluating unconventional resources including organic mudstones and tight siltstones. Part 1 reviewed the unique challenges and provided an overview of the proposed workflow (Newsham et al., 2019). Part 2 describes in detail the many components of the workflow and how they come together to determine the storage capacity of the reservoir. Part 3 links the petrophysical results to the production potential in terms of fractional flow and water cut and will present alternate cross-checks of the storage properties to validate the results.
As stated in Part 1, one of the most important functions that the petrophysicist provides is the estimation of accurate storage properties. However, when the authors survey the range of workflows used to estimate the storage capacity of these complex systems, we find a wide range of options. Solutions can vary from simple deterministic to more complex probabilistic approaches. Whatever the method, the objective should be the same: to provide consistent, portable hence reliable estimation of hydrocarbon storage capacity, also known as “Petrophysics CPR.” As mentioned in Part 1, estimation of hydrocarbon storage is more than just the calculation of porosity and water saturation. In this tutorial, we will describe a workflow that has been successfully used to evaluate thousands of wells in the Permian Basin with great consistency. The authors have nearly 100 wells with core data to calibrate the workflow. We will show examples of the workflow’s portability by highlighting examples from the Midland Basin, the Texas Delaware Basin and the New Mexico Delaware Basin. We will show how every property measured in core matches to log-based profiles using a combination of deterministic and the constrained simultaneous solution methods. The workflow also is found to be reliable in other basins throughout the world, however, the examples will be confined to the Permian Basins.
This is a three-part tutorial of a workflow for evaluating unconventional resources including organic mudstones and tight siltstones. Part 1 reviews the unique challenges and we provide an overview of the proposed workflow. Part 2 describes in more detail the many components of the workflow and how they come together to determine the storage capacity of the reservoir. Finally, Part 3 links the petrophysical results to the production potential in terms of fractional flow and water cut.
One of the most important functions that the petrophysicist provides is the estimation of accurate storage properties. In the oil and gas industry, storage defines the opportunity, and flow pays the bills. Estimation of storage is more than just estimation of porosity and water saturation. It begins with accurate assessment of rock composition which begets accurate porosity and subsequently water saturation. However, storage estimation need not end there. With an understanding of fluid type and properties, and with the application of appropriate equations of state that describe the variation of formation volume factor, bubblepoint or dewpoint pressure, oil viscosity and density as a function of temperature, pressure, GOR, API gravity and gas gravity, very accurate assessments of oil in place (OIP), gas in place (GIP), and water in place (WIP) are possible in profile. These profiles are then integrated into cumulative storage volumes by bench.