Session 1 
Wednesday, August 5th
8:00am – 9:00am US Central Time

8:00 AM
Comprehensive Model for Microfrac Test and Case Study from Deep Water Gulf of Mexico

Guoqing, L. Ehlig-Economides, C., Cedillo, G. and Wilson Pineda, University of Houston / BP

The microfrac test is commonly used to measure the stress profile through reservoir zones or seal rocks. Currently used models or approaches in microfrac analyses are related to those used to analyze a minifrac test or a diagnostic fracture injection test (DFIT). However, those models do not consider some specific features of the microfrac test. It is common to see jobs that fail to initiate a fracture or that yield uncertain fracture closure quantification. This presentation shows a novel model specifically derived for the microfrac test.

Unlike the traditional models that only focus on the dynamic of the created hydraulic fracture, the proposed comprehensive model includes the isolated wellbore. In the material balance function for the system, the total injected volume consists of four components: wellbore fluid volume compression caused by pressurization, fracture volume, and leakoff volumes through the wellbore and the fracture, respectively.

The model highlights the difference between the microfrac test and the traditional minifrac test or DFIT. Wellbore leakoff must be considered in microfrac design and post job analysis. It can represent comparable or even larger leakoff area than the created hydraulic fracture. Other key parameters that determine the fracture size and closure time include the injected volume, rock elasticity, the fluid leakoff coefficient through hydraulic fracture, and fracture net pressure. Additionally, the work includes a new approach to identify fracture initiation during pumping.

The comprehensive model is the first one developed specifically for the microfrac modelling. It is intended for microfrac design and post job analyses.  This presentation will show the theory and illustrate the analysis using Gulf of Mexico data.

8:30 AM
Deep Transient Testing - Dubost, F.  - Schlumberger

Francois Xavier Dubost - Reservoir Engineer Advisor with Schlumberger, Francois graduated from Herriot Watt University with a Master's degree in Petroleum Engineering. His current responsibilities are in the technical support of reservoir engineering services throughout Mexico, Central America and offshore North America. François has worked on different continents for the past 25 years with Schlumberger, with experience in logging, operations management and interpretation engineering. His technical expertise lies in transient test interpretation, fluids and sampling. He also has previous experience in reservoir studies, such as field development planning and production optimization studies, having worked for five years in the Schlumberger consulting line. Francois is a member of the SPE and SPWLA societies.

ABSTRACT: Appraisal activities for offshore reservoirs require detailed data acquisition to reduce subsurface uncertainties and support evaluation of development alternatives. Investment in strategic formation evaluation enables refining reserves estimates, robust development decisions, and construction of a Field Development Plan (FDP) that considers the full range of outcomes and provides flexibility to both mitigate downside and capture upside potential.

Reservoir testing is a critical component of the reservoir evaluation in Exploration or Appraisal due to its direct impact on project’s key economic parameters. However, a conventional well test involves a complex logistical framework, completing the well, perforating, flowing the well to surface and disposing at surface of the produced fluid. In Mexico, this requires renting a disposal boat and represents high costs and potential environmental concerns.

Wireline Formation Testing (WFT) has matured as Operators and Service Companies have been exploring ways to de-risk reservoir evaluation with such systems, while reducing times and costs of testing without compromising the requirements for high quality information.

Recently, Deep Transient Testing (DTT) techniques have been developed as an alternative to conventional testing, supplying an environmentally friendly way of evaluating thick reservoirs and lower costs.

The technique has been developed to obtain uncontaminated samples of reservoir fluids and test layer by layer stacked reservoirs with larger production of hydrocarbon volumes and transient times compared to previous WFT systems. DTT allows extended depths of investigation and the ability to individually evaluate a large number of different zones but requires careful planning and handling of produced fluids for well control purposes in newly drilled open hole wells. 

This presentation will aim at describing the DTT technique, discuss the simulation steps to plan such test and show a couple of case studies from offshore Mexico. In the discussion, elements of the new platform permitting to conduct such tests will also be exposed.

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