The project goal is to develop a new Low Frequency Electromagnetic Induction 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. The proposed low frequency electromagnetic induction tool can be used to detect far-field anomalies in the rock matrix from a single borehole.
The University of Texas at Austin, Austin, TX 78712
E-Spectrum Technologies, San Antonio, TX 78249
Hydraulic fracturing has become a major driver for unconventional oil and gas production in the United States. Knowledge of hydraulic fracture dimensions is of great importance when predicting production, validating reservoir and fracture models, and improving production economics. However, we still lack an inexpensive, direct, and repeatable post-fracturing diagnostic tool to measure the dimensions and orientation of propped hydraulic fractures. Project researchers will build and test a prototype for 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.
The project team anticipates that the proposed technology will be a game changer in fracture diagnostics because it is inexpensive, repeatable, and fairly simple to operate. In addition to the key critical advantages mentioned above, the proposed technology can offer the following benefits consistent with DOE’s ongoing efforts:
The direct inversion algorithm is used to quickly invert the data and calculate the area, conductance, and dip-angle of a single fracture in a few minutes. The algorithm is based on the approximation used to calculate surface currents without solving the linear system of equations. The resolution of inverted parameters was shown to be very satisfactory for field deployment in open-hole wells.
Coaxial, co-planar and cross-polarized transmitters and receivers have been built and tested in the lab and in a near surface well. Both the lab results and the near-surface test on the prototype tool that were completed clearly show that the tool response is in very good agreement with the model results. The results also show that it is feasible to map fractures in the subsurface with the transmitters and receivers that have been built with excellent signal to noise ratio.
These results pave the way for building the electronics and transmitters and receivers for a downhole tool. Currently the prototype tool is being driven by external electronics and hardware. Modeling of the induction tool was completed and the results indicated that an EM tool would work well in open-hole completions. The design of the induction tool was changed substantially based on the new simulations. The new improved design is much more compact than the original design.
Lab measurements were made for the electrical conductivity of mixtures of proppant and sand. It was found that the electrical conductivity remained high even for a 50:50 mixture of sand and petroleum coke. The fracture conductivity of such mixtures was measured to be less stress sensitive. Values of the proppant conductivity were found to be 2,000 to 5,000 times larger than the shale conductivity. This means that mixtures of sand and proppant can be used as a proppant.
Current and future work is focused on four main remaining tasks:
Fracture Diagnostics Using Low Frequency Electromagnetic Induction And Electrically Conductive Properties (Aug 2017)
Presented by Mukul Sharma, University of Texas at Austin, 2017 Carbon Storage and Oil and Natural Gas Technologies Review Meeting, Pittsburgh, PA
Fracture Diagnostics Using Low Frequency Electromagnetic Induction And Electrically Conductive Properties (Aug 2016)
Presented by Mukul Sharma, University of Texas at Austin, 2016 Carbon Storage and Oil and Natural Gas Technologies Review Meeting, Pittsburgh, PA