08123-07

Goal
The goal of this project is to investigate a new, “mini-waterflood” strategy for enhancing oil recovery from small, mature fields. The project combines reservoir simulation and core displacement studies to evaluate the feasibility of the mini-flood concept. The broader objective is to provide small producers with knowledge and tools needed to improve recovery and extend the life of small, depleted oil fields.

Performers
New Mexico Institute of Mining and Technology (NMIMT), Socorro, NM 87801
Armstrong Energy Corporation, Roswell, NM 88202

Background
Many small oil fields are not well suited to conventional practices of patterned waterflooding. The oil-bearing reservoirs may be small, thin, and shallow, with low reservoir pressure and unfavorable mobility ratios. Many of these small plays have been developed by independents and small producers who lack the technical and financial resources to implement extensive secondary recovery efforts. Typically, these reservoirs are shallow discoveries that were made after deeper targets proved non-productive. In many cases, current production is barely maintaining lease ownership.

This project was formulated to address the potential for secondary recovery in such reservoirs. The approach is to test a mini-waterflood concept that may provide a cost-effective option for pressure maintenance and improved sweep efficiency in these fields.

A mini-waterflood is not a fully-developed, patterned waterflood but rather a non-traditional water injection program to provide pressure maintenance and improve sweep efficiency in reservoirs that are thin in thickness, shallow, at relatively low pressure and temperature, and have unfavorable mobility ratios. The concept involves injecting water in targeted areas to improve oil recovery and extend the reservoir life.

The project focuses on the Queen Sand in the Round Tank Field of Southeast New Mexico, where preliminary reservoir characterization and modeling were carried out in the 1990’s. The Queen Sand is known to have high potential for secondary recovery. Queen Sand reservoirs in this area are comprised of a series of interlayered porous sands, oriented along a northeast-southwest trend. Porosity terminates updip and downdip in each sand body, creating multiple stratigraphic traps with separate hydrocarbon and water contacts in each.

During this project, experimental core displacement studies will provide a quantitative measure of the mobile oil available for secondary recovery. Reservoir simulation will investigate a range of injection rates and pressures, and ultimately be used to recommend a development and injection plan based on what is most favorable for oil recovery. If successful, the project’s results are likely to be applied in application of similar projects in adjacent fields with similar characteristics and similar potential for secondary recovery.

The project is led by NMIMT, in partnership with Armstrong Energy, a small independent operator in Southeast New Mexico. Armstrong Energy is providing technical expertise and core samples for laboratory studies, and will also drill up to two test wells in the Queen Sand depending on the technical results of the experimental and modeling efforts. Keltic Well Services, a small wireline company, will provide static pressure buildup measurements in both existing and new wells. The main deliverable for this project will be a Final Report detailing all technical results of the project.

Potential Impacts
Locally, this project should lead to increased oil recovery in the Round Tank/ Queen Field, with 500 to 1250 MBO in added reserves expected. Regionally, based on the generation of interest on the part of other operators due to this research, it is likely that adjacent Queen Sand fields will become targets for secondary recovery, leading to additional incremental oil reserves.

Increased domestic oil production would result in increased tax revenues, royalties, and regional economic benefits. Improved recovery from existing wells has the added benefit of decreasing the environmental footprint of an overall field development program.

Accomplishments
This project began in August 2009. Both the Project Management Plan and the Technology Status Assessment have been completed. The Project Management Plan consists of a work breakdown structure that concisely addresses the objectives and approach for each task with all major milestones and decision points. The Technology Status Assessment describes the state-of-the-art of the proposed technology.

Through core analysis, NMIMT discovered that permeability decreased over time during core displacement experiments. The cause of this phenomenon was determined to be fines migration; minor clay swelling is also a potential cause.

NMIMT has assembled a digitized log database and a production database from paper copies. The Queen formation has been represented as having three layers based on gamma ray and porosity logs. Production history from all the wells producing from the Queen formation has been collected and converted into a form suitable for simulation.

The variable mechanical properties of the Queen formation seen in the core and logs, and the presence of clays and fines migration, have implications on both hydraulic fracturing and water injection. For this reason, an investigation into the stimulation effectiveness of the injection well (RTQU #7) was initiated (after stimulation of the well there was no improvement as the water failed to flow through the formation). A tracer log was run by Schlumberger to give insight to the fracture height and to understand the fluid and proppant distributions within the fracture. Results will also assist the reservoir characterization and modeling efforts.

A basic reservoir model framework has been developed. The model is 4 sections x 4 sections x 3 layers, 120 x 120 x 3 grid blocks. Porosity-permeability correlations have been developed for the various layers of the formation the simulation model. Reservoir modeling is continuing.

Current Status (January 2011)
The key tasks to be undertaken are outlined below.

Core Displacement Studies – The research team will analyze Queen Sand core porosity, permeability, saturations, and lithology, and will analyze reservoir fluid gravity, density, and viscosity. The researchers will select a suite of samples for analysis of oil recovery as a function of water injection parameters under approximate reservoir conditions. Relative permeability curves will be developed for input into a reservoir simulator.

Reservoir Model Development – The researchers will construct a reservoir model for the Queen Sand reservoir using the core information obtained in the preceding task, along with available production, pressure, petrophysical, and geologic information. This will require analysis of well logs, production data, geologic tops, geologic structure, and static pressure data from existing wells.

Reservoir Performance Prediction – The project team will carry out reservoir simulation runs in an effort to predict reservoir performance for the Queen Sand. Automatic history matching will allow for data adjustments of the least known variables. Consultation with Armstrong Energy technical staff will provide information needed to history-match the reservoir simulations. Finally, the researchers will use the simulation model to predict future reservoir performance for a variety of water-flood strategies. The analysts will vary injection and production well placement, injection rates, and pressures to optimize incremental oil recovery.

Technology Transfer – NMIMT will develop and implement an effective program for technology transfer. Project results will be communicated to industry via presentations and technical articles, first locally and then more regionally. On the local level, presentations and papers will be given at meetings of the Roswell Geological Society and Roswell Section of the Society of Petroleum Engineers (SPE), to reach targeted industry representatives. More regional presentations and articles may be given at Permian Basin and regional SPE meetings. The final step would be to present project results at a national conference organized by SPE, American Association of Petroleum Geologists, or RPSEA.

Project Start: August 5, 2009
Project End: August 4, 2011

DOE Contribution: $313,751
Performer Contribution: $88,716

Contact Information:
RPSEA – Martha Cather (martha@prrc.nmt.edu or 575-835-5685)
NETL – Chandra Nautiyal (chandra.nautiyal@netl.doe.gov or 918-699-2021)
NMIMT – Thomas Engler (engler@nmt.edu or 575-835-5207)

Additional Information:

Final Project Report [PDF-13.1MB]