Affiliation:
1. School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
3. Research Institute of Exploration & Development, PetroChina Changqing Oilfield, Xi’an 710018, China
4. Engineering Supervision Department, PetroChina Changqing Oilfield, Xi’an 710018, China
Abstract
The role of the horizontal well in developing unconventional oil and gas reservoirs is particularly significant. Different from vertical wells, horizontal wells are greatly affected by many factors, e.g., well track, surrounding mudstone, resistivity, and pore structure heterogeneity in horizontal and vertical directions. These make it difficult to evaluate reservoir parameters and determine optimized test layers. In order to improve formation evaluation in horizontal wells, it is necessary to carry out the research of analyzing formation anisotropy, predict physical property parameters, and classify formation to determine high-quality intervals. In this study, taking Triassic Chang 8 Formation in Shunning Region, Central Ordos Basin as an example, 40 core samples were drilled and applied for nuclear magnetic resonance (NMR), mercury injection capillary pressure (MICP), and resistivity experiments. The porosity, permeability, resistivity, and pore structure anisotropy are analyzed. Results illustrate that the physical properties and pore structure in horizontal direction are superior to vertical direction. Meanwhile, NMR log loses its role in pore structure characterization in horizontal wells. Afterward, methods of correcting interval transit time (DT) and resistivity anisotropy are raised, and models of predicting formation physical property parameters, such as porosity, permeability, and water saturation, are established. A parameter, named as the formation type indicator (FTI), is proposed to reflect reservoir oil-bearing properties and pore structure. Finally, our target horizontal intervals are classified into four types, and the highest-quality “sweet spot” is determined.
Funder
National Natural Science Foundation of China
China Postdoctoral Science Foundation
Fundamental Research Funds for the Central Universities, China
MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences
Subject
Process Chemistry and Technology,Chemical Engineering (miscellaneous),Bioengineering
Reference44 articles.
1. The challenge of logging horizontal wells;Clavier;Log Anal.,1991
2. Relationship between horizontal well trajectory and formation analysis in Longdong tight oil area;Liu;J. S. Pet. Univ. (Sci. Technol. Ed.),2017
3. Zhang, P. (2016). Research on Horizontal Well Formation Evaluation Method Based on Acoustic and Resistivity Logging. [Master’s Dissertation, China University of Petroleum].
4. Technology review on the log interpretation of horizontal well;Zhou;Prog. Geophys.,2006
5. Seepage characteristics and productivity distribution of segmented multi-cluster fractured horizontal wells;Ren;J. Xi’an Shiyou Univ. (Nat. Sci. Ed.),2013