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Porosity Evolution of Shale in the Burial History

Qiulin Guo¹, Xiaoming Chen¹, Huanqi Song², Man Zheng¹, and Jinliang Huang¹
¹RIPED, PetroChina, Beijing, China
²China University Of Petroleum, Beijing, China

In this paper we counted and analyzed shale porosity data of eighteen foreign authors’ literatures, thirty-seven measured cores in four basins of China, logging interpretation of six wells of five regions and three different kinds of experimental simulation results. Through comparison and verification, the analyses show the trends of shale porosity evolution in burial history and the difference of porosity evolution processes. we discussed three reasons which caused the difference: (1)The sample data of four basins proved that the over-pressure caused by organic-rich source rock in hydrocarbon generation processes slows down the porosity decrescent rate, is one factor why shale remains relatively high porosity value in middle-deep depth, and also contributes 11% in average to the increase of porosity; (2)After analyzing forty-two NOM(Nanopore originating in organic matter)data, we think that the NOM generated in hydrocarbon generation processes is another important factor which made the porosity of organic-rich shale increase, and contributes 0.9% in average to the increase of porosity; (3)Through testing 23 samples, we confirm that the porosity in brittle mineral is 2%, smaller than the one in isometric clay minerals, and its contribution is only 1.3%, the results illustrate that the dissolution affects little to shale porosity growth. Based on the above observations, We built three-stage normal compaction model, under-compaction model and NOM correction model, and analyzed the key parameters of the model and proposed an estimation template of the percent of area pores in organic matter. Applications showed that the models have practical value, and are useful to the development of unconventional resources assessment and exploration technology.

AAPG Search and Discovery Article #90175©2013 AAPG Hedberg Conference, Beijing, China, April 21-24, 2013