Determination of geomechanical parameters based on well logging data

UDK: 622.
DOI: 10.24887/0028-2448-2017-6-30-33
Key words: variable density logging, full waveform sonic logging, geomechanical parameters, synthetic log curves, fracture treatment
Authors: O.V. Salimov (TatNIPIneft, RF, Bugulma)

Establishing correlations between well logging data and geomechanical parameters is a top priority task. In future, this will enable determination of geomechanical parameters directly from well logs, thus resulting in improved fracture treatment designs.

Problems associated with generation of synthetic well logs have been considered together with available solutions. Criteria for generalization of regression equations have been evaluated. The research has relied on heuristic approach which is an expert based analysis that has been used to select and generalize equations for characterization of a group of wells located within some production area. The equations have been selected for value averaging when correlation coefficients have been high enough compared to general values observed, while the cross-plot has exhibited no shape anomalies.

This research has involved analysis of distortions observed on variable density and full waveform sonic logs as well as their effects. A method to adjust sonic log curves based on gamma ray log readings is proposed. Recommendations for adjustment of formation density logs are provided. Formulas for estimation of synthetic curves for P- and S-waves interval transit times versus other geophysical parameters have been obtained. The need for geophysical data quality control is highlighted.

Cross plots have been created, regression equations between Young’s modulus and geophysical data have been solved. Summary equations for Young’s modulus and well log data for Tatarstan oil fields have been obtained. It has been demonstrated that synthetic well logs are required for estimation of Poisson’s ratio. Absence of correlation between gamma-ray data and Poison’s ratio has suggested that geomechanical cross-sections constructed without account of full waveform sonic log data and with consideration of full waveform sonic log data differ substantially. Recommendations for application of the resulting petrophysical relationships to design efficient fracture treatments are provided.


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