Cuttings-test method for predicting rock strength

Abstract

In drilling engineering, it is an urgent technical problem to obtain the rock mechanical parameters of the drilled formation in time and accurately. Rock cuttings is another form formed after rock is broken. Rock cuttings contain some physical properties of the original rock. Taking cuttings as the object of research, this paper puts forward the penetration test featuring “penetrating without fracture” to test penetrating depth using acicular indenter so as to demonstrate parameters of rock mechanics. Experimental study showed that if the rock did not crack, under a certain load, the depth of cuttings is correlated with the uniaxial compressive strength and hardness of primeval rock. In the paper, models of relationship between penetrating depth and uniaxial compressive strength of primeval rocks, and between the penetrating depth and hardness of primeval rocks were established, and were verified by experiment. The error of experimental results is small. The method of “penetrating without fracture” can reduce the dispersion of test data of cuttings, leading to high accuracy of calculation model. This method is an effective way to obtain the parameters of rock mechanics of formation in drilling timely and accurately.

Keywords

• Cuttings
• Rock mechanics
• Penetrating
• Formation
• Experiments