FRACTURE DIAGNOSTICS USING LOW FREQUENCY ELECTROMAGNETIC INDUCTION AND ELECTRICALLY CONDUCTIVE PROPPANTS

Project Objectives:

Hydraulic fracturing has become a major driver for unconventional oil and gas production in United States land operations. Knowledge of hydraulic fracture dimensions is of great importance when it comes to predicting production and validating reservoir and fracture models; and ultimately, improving production economics. However, we still lack a cheap, direct and repeatable post-fracturing diagnostic tool to measure the dimensions and orientation of propped hydraulic fractures. Our primary objective is to build and test a downhole fracture diagnostic tool that can be used to estimate the orientation and length of the ‘propped’ fracture (not the created fractures), since this is the primary driver for well productivity.

This research investigates a new Low Frequency Electromagnetic Induction (LFEI) method which has the potential to estimate not only the propped length, height and orientation of hydraulic fractures but also the vertical distribution of proppant within the fracture. Our past modeling research has shown that measuring the propped fracture dimensions and orientation is possible with the use of a low frequency downhole logging tool in conjunction with an electrically conductive proppant. The proposed low frequency electromagnetic induction tool can be used to detect far field anomalies in the rock matrix from a single borehole. The anomaly (in our case, hydraulic fracture) will be a filled with a contrasting agent (in our case the conductive proppant). The proposed tool has one tri-directional transmitter and three tri-directional receiver sets, each with a bucking coil to cancel out direct coupling. Electrically conductive proppants are currently available in the market, which can be used to offer a dielectric (either magnetic, or conductive or both) contrast that can make the signal received even more pronounced. This received signal can then be analyzed to infer the geometry of the hydraulic fracture.

The proposed work will be conducted in seven Tasks as outlined below.

Task 1: Project Management Plan
Task 2: Development of forward model using proposed tool and different fracture geometries
Task 3: Lab testing of available proppants in the market for electrical and material properties
Task 4: Construction of low frequency electromagnetic tool
Task 5: Field testing of tool
Task 6: Inverting the obtained field data for simulated rock volume (SRV) map
The proposed technology has the following key advantages, which is not presently offered by any technology in the market:

1. It can be executed from a single wellbore.
2. It is a direct far field measurement.
3. This tool can be run in hole after hydraulic fracturing. If the need arises, it can be used at any time during the well’s life cycle providing a time lapse analysis of fracture growth or closure.
4. Since it obtains tri-directional signals, these tensors can be resolved to obtain a simulated volume map, which can be correlated directly to the productivity of a given well.
5. This is the only technology that can obtain propped fracture length, which governs well productivity. Also it can be used to detect proppant banking in the hydraulic fracture.

We anticipate that the proposed technology will be a game changer for in fracture diagnostics as it is cheap, repeatable, and fairly simple to run. In addition to key critical advantages mentioned above the proposed technology can also offer the following benefits which as in line with DOE’s ongoing efforts:

1. Additional recovery: This tool can improve our understanding of true simulated rock volume, since it tracks propped volume of hydraulic fractures and not shear slip events during a fracturing job. Therefore, using this technology, we can model the reservoir better and find effective re-fracturing candidates. Also a true simulated rock volume map can help us design better simulations for subsequent wells.
2. Reduced costs: This tool can be operated at any time during the well’s life cycle and not necessarily during the hydraulic fracturing job (as is the case with microseismic monitoring). Therefore, it will be reduce the equipment load during a fracturing job, thereby reducing the environmental footprint. Since this technology, being a single wellbore application, doesn’t require a monitoring well, it can be potentially deployed in any hydraulically fractured well with or without a rig (can be deployed with a MAST truck).  Due to the simplicity of deployment and ease of operation, we anticipate a much reduced cost as compared to microseismic monitoring while providing more reliable results.
3. Environmental benefits: This technology basically tracks the location of conductive proppant using the proposed electromagnetic logging tool. Therefore, it can used to track if the fractures are hydraulically connected to natural aquifers. This tool can be run alongside Cement Bond Logs, in fractured reservoirs to ensure hydraulic isolation of oil and gas producing zones. Also the inverted product of this data can be combined with other geophysical data (2D and 3D seismic and/or CSEM data) to find connections with natural fractures.

Participants involved in the project: