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Abstract Rock core discing is a kind of unique phenomena that occurs in environment with high geostresses. Both practical observation and theoretical analysis state that there is an inner relation between geostresses and the degree of rock core discing. Because it is difficult to measure geostresses in above environment，it has remarkable meanings in estimating geostresses by rock core discing. There is a complex mechanical process in rock discing，whose calculation formula and theory are very immature. The paper simulates how different geostresses affect the degree of rock core discing，stating that different geostresses induce different failure patterns of rock core，and the discing can be induced by the action of either shearing or tension. Then the paper proposes a calculation method of safety degree of elements located in potential failure surface of rock core combining elastic finite element method and Mohr-Coloumb criterion with tension limitation. The element safety degree distribution of potential surface can be displayed by element safety degree method，and can reflect the relation between geostresses and discing thickness. Based on the relation，the observation of rock core can be used to feed-back analyze original geostresses. By simulation based on element safety method，corresponding to different vertical stresses while the horizontal stresses being fixed，the safety of element degree distribution and the failure pattern of rock core are gotten. Using the method to analyze the geostress and rock core of Bakken formation in Williston Basin in USA，the results of calculation and observation are identical，which shows the method is feasible.
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Received: 10 January 2010
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