[BH-P-01] Anisotropy Based Wireline Logging Data Normalization in Shale Gas Horizontal wells and Customized Formation Evaluation in Changning Shale Gas Field
The strong demand for energy resources requires exploration of unconventional resources in China. Dozens of horizontals wells are drilled in shale gas reservoirs in Changning area every year, and the differences of logging responses of vertical and horizontal wells have brought uncertainty in formation evaluation.
A customized core experiment workflow is implemented to calibrate the petrophysical properties derived from wireline measurements in the vertical wells, such as triple combos, spectroscopy, dipole sonic, borehole images, and nuclear magnetic resonance (NMR). The logs acquired in the horizontal wells need to be normalized, since the petrophysical models are built in the vertical wells. It is difficult to normalize the compressional slowness acquired in the horizontal well (DT_H) to that in the vertical well, because the difference of the slowness is controlled by many factors. This paper presents an innovated way to get the verticalized compression slowness (DT_V) in the horizontal wells, which incorporate core slowness experiments in big data database, shear anisotropy derived from dipole sonic measurement, borehole trajectory and formation bed boundary derived from borehole images.
Case studies are presented in the Changning shale gas field of PetroChina, which is in the Sichuan Basin of China. In the horizontal wells, the verticalized DT_V decreases about 5-10 us/ft when comparing with the measured DT_H. The DT_V matches perfectly with the compressional slowness of the same zone measured in the vertical pilot hole. It greatly lowers the uncertainty when performing the formation evaluation in the horizontal wells. Ion-milled backscatter scanning electron microscope (BSE) reveals the pore structure of the shale gas reservoir. The pore spaces are dominated by organic pores relating to kerogen, and in-organic pores relating to minerals, such as quartz and clay. The core-validated petrophysical properties of formation elements, lithology, porosity, permeability, total organic carbon content (TOC), gas content, and fluid saturation alleviate the uncertainties in determining the best zones.
This paper discusses a novel application of anisotropy based wireline logging data normalization workflow and formation evaluation of shale gas reservoirs, which helps the operator find the sweet spot.
A customized core experiment workflow is implemented to calibrate the petrophysical properties derived from wireline measurements in the vertical wells, such as triple combos, spectroscopy, dipole sonic, borehole images, and nuclear magnetic resonance (NMR). The logs acquired in the horizontal wells need to be normalized, since the petrophysical models are built in the vertical wells. It is difficult to normalize the compressional slowness acquired in the horizontal well (DT_H) to that in the vertical well, because the difference of the slowness is controlled by many factors. This paper presents an innovated way to get the verticalized compression slowness (DT_V) in the horizontal wells, which incorporate core slowness experiments in big data database, shear anisotropy derived from dipole sonic measurement, borehole trajectory and formation bed boundary derived from borehole images.
Case studies are presented in the Changning shale gas field of PetroChina, which is in the Sichuan Basin of China. In the horizontal wells, the verticalized DT_V decreases about 5-10 us/ft when comparing with the measured DT_H. The DT_V matches perfectly with the compressional slowness of the same zone measured in the vertical pilot hole. It greatly lowers the uncertainty when performing the formation evaluation in the horizontal wells. Ion-milled backscatter scanning electron microscope (BSE) reveals the pore structure of the shale gas reservoir. The pore spaces are dominated by organic pores relating to kerogen, and in-organic pores relating to minerals, such as quartz and clay. The core-validated petrophysical properties of formation elements, lithology, porosity, permeability, total organic carbon content (TOC), gas content, and fluid saturation alleviate the uncertainties in determining the best zones.
This paper discusses a novel application of anisotropy based wireline logging data normalization workflow and formation evaluation of shale gas reservoirs, which helps the operator find the sweet spot.
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