Mexico Unconventional Recourses and Micro-Seismic Studies
Authors: Weimann Mauro Iván , Lopez Martinez Christian , Monroy Santiago Faustino , Salazar Juarez Josue 
Published: October 2018

In 2014 Mexico's Energy Reform set a series of challenges for the country, the industry has undergone a profound transformation, and during the last years, different projects were done to address these situations. In this work we want to briefly highlight the main conclusion and findings obtained from three main projects that set part of the rules for the future of unconventional in Mexico: one about the hydrocarbon unconventional resources, other about the new regulatory framework, and finally a specific technical project about the micro-seismic performed on an unconventional well.

An important amount of information was obtained during the extensive history of the oil and gas Mexican industry, this information was always focus on the conventional reservoir, therefore a strong effort was done to adequate this data and evaluate the potential unconventional resources. In this work we want to present most important conclusion obtained from this resources study.

In this work we also want to present a technical work about the micro-seismic result obtained from an unconventional well in Mexico: micro-seismic interpretation is not a straightforward process. It generally presents different challenges and particularities, such us abnormal behaviors that should be addressed with different interpretation tools. During this stage, the effort is focused on conciliating the theory behind the generation and detection of micro-seismic events and the theory of hydraulic fracturing for conventional and unconventional reservoirs, and explains any deviation from this conciliation. Finally, the integration of all the information available (well logs, surface seismic, structural model, geology, petrophysics, geomechanics, etc.) is a crucial step toward the final interpretation of the micro-seismic event patterns.

This technical study focuses on challenges and particularities found during the analysis, interpretation and evaluation of the micro-seismic mapping recorded on a horizontal exploratory well in northern México.

This microseismic mapping showed excellent results, with more than 22,400 events detected during the pumping of 11 stages along the horizontal section. Many abnormal behaviors were observed, and hard work was made to calibrate velocity model and reduce uncertainties of micro-seismic event location.

Analysis of the final processing results determined that 98% of these events are related to the activation of pre-existing planes of weakness within an upper formation (outside the target formation). Integrated data showed the faulting was due to a fold structure.

The application of different interpretation tools and filters permitted the remaining 2% of microseismic events directly related to the hydraulic fractures to be selected. At last, these microseismic event patterns were interpreted using unconventional fracture models, allowing the characterization of fracture network geometries and volumes. The final evaluation results were compared with the initial fracture network designs, enabling accurate calibration of models for future jobs.

Conclusion and lessons learn obtained during this process are associated to microseismic monitoring condition and limitation for this job (structure influences, formation texture and properties, etc), characterization of the fracture network (geometries, coverage), efficiency of the multi-stage fracturing job and recommendation for future works.