The Piceance Basin is an asymmetrical sedimentary basin in the northeast part of the Colorado Plateau. The basin is highly asymmetric with steeply dipping strata on the eastern flank and gently dipping strata on the southern, western, and northeastern portions. The basin’s synclinal axis trends northwest to southeast close to the eastern edge of the basin. Currently, 38 oil and gas fields have been discovered, and of these, 21 produce partially or completely from basin-centered gas accumulations.
PhD student Yao Tong is working on an interdisciplinary project under BPSM and SCRF (Stanford Center for Reservoir Forecasting). The first phase of her project involves the development of a three-dimensional basin and petroleum system model of the Piceance Basin. Four major total petroleum systems contribute hydrocarbons to the Piceance Basin: Phosphoria, Mancos-Mowry, Mesaverde and Green River petroleum systems, distinguished by different source rocks found in each system. In this study, we will first focus on modeling the Mesaverde petroleum system in the 3D conceptual model, because the Mesaverde petroleum system is the major contributor of gas produced from the Piceance Basin over the past several decades.
The following are the three main research tasks and objectives we plan to investigate in this study:
A. Follow a standard BPSM workflow to create a robust time-to-depth velocity conversion and build a regional 3-D basin model from basement to topography and focusing on the Cameo Coal source rock, while modeling the four essential petroleum system elements.
B. Evaluate possible geologic scenarios for the relative contributions of each source rock to the total hydrocarbon accumulations of the basin.
C. Evaluate the possibility of the basin-centered gas concept, as introduced in the previous section, using our 3D model to facilitate testing of different geologic scenarios.
For Task B, the initial choice of possible scenarios will be based on three different major source-rock map inputs:
- The Cameo Coal source rock is the thickest and most widespread coal, developed in the coastal-plain strata above the thick and laterally extensive Rollins shoreline sandstone.
- The Upper Cretaceous Mancos Shale is a potential marine shale source rock that underlies the Mesaverde Group.
- The Niobrara Shale is an even deeper possible source rock. We will investigate beyond the Mesaverde petroleum system; however the gas resources generated from the Niobrara either have migrated vertically or are still trapped in the Niobrara Formation. We will explore how much gas was captured in the BCGA and how much may have escaped from the entire basin.
For Task C, a regional study and investigation of the pore-fluid pressure, fracture growth timing associated with temperature, pressure, and fluid-composition conditions from thermal history will be helpful to address the debate of the BCGA concept.
We started our investigation by studying the Cameo Coal source rock and built the 1D model at the Mobil Oil T-52-19-G well location. This well is located in the structural trough of the Piceance Basin. The Cameo Coal source rock has total organic carbon (TOC) of 50%, and hydrogen index (HI) of 150 mgHC/gTOC. The kinetic model for this 1D model is Pepper and Corvi (1995) D/E Type III. At this well location, the source rock was deeply buried and was heated to the gas window. The Cameo Coal started to generate gas about 48 Ma and continued until about 10Ma, when a major episode of uplift began.
Building on initial modeling efforts, we will construct a 3D model using as a basis six horizons mapped with seismic and well data. Besides the seismic information, we have 231 wells with formation top information, which will be very useful for constructing the depth maps for the additional horizons.