Geological Characteristics and Identification Standards of High Production Horizontal Wells Target Layers in Shale Reservoir

Abstract

There are various types of continental shale oil reservoirs in China, with breakthroughs in multiple basins such as Ordos and Junggar. From the perspective of production efficiency, not only are there significant differences in different regions, but also the same reservoir transformation technology is used for the same region and small layer. If there are changes in the target layer of horizontal wells, it will have a huge impact on production. Therefore, clarifying the characteristics and identification criteria of high yield target layers in horizontal wells of shale reservoirs is of great significance for rapid production and efficient development of shale reservoirs.The development of shale oil reservoirs in China started relatively late. Drawing on the experience of the shale oil and gas revolution in North America and the rapid production of shale gas in China, the horizontal well target layer of shale oil reservoirs is generally selected in the interval with high TOC and good compressibility, but the implementation effect is not ideal, and the characteristics and identification standards of the high production target layer of horizontal wells have not been established.By analyzing the main production areas of shale oil reservoirs in North America and comparing the production effects of different target horizontal wells in multiple shale oil regions in China, such as Gulong, Yingxiongling, and Cangdong, it is clear that the high yield target layers of horizontal wells are characterized by oil and gas enrichment layers (medium and high resistivity) with developed large pores and good effectiveness of bedding fractures (fracture development) under the background of medium and high TOC, and have good roof sealing conditions. Due to the complex geological conditions of continental shale oil in China, there should be differences in target identification standards among different regions. Taking Gulong and Yingxiongling shale oil as examples, a classification and evaluation standard for target layers has been established. The key parameters of Gulong are medium to high resistance (>5 ohmmeters), AC-RT and AC-CNL intersect with a certain envelope surface, and the cut-off value of nuclear magnetic resonance logging at 35ms has a porosity greater than 2%; The key parameter of Hero Ridge is that the lithology is layered limestone, with low GR (<95API) and low resistance (<15 ohmmeters). The cutoff value of nuclear magnetic resonance logging is 33ms, and the porosity is greater than 6%..

Copyright 2023, IFEDC Organizing Committee.

This paper was prepared for presentation at the 2023 International Field Exploration and Development Conference in Wuhan, China, 20–22 September 2023.

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