Experimental research on dependence of penetration rate on diamond exposure at bit face and drilling parameters

Abstract:

Russian drilling specialists have proposed such an idea that in normal diamond drilling the quantity of produced cuttings should be correspond to the quantity of cuttings discharged by the drilling fluid, otherwise the cuttings will fill the bottom of the hole, forming “cuttings cushion” and obstructing rock fragmentation. Therefore, in designing the drill bit and defining the drilling parameters, equality between the volume of produced cutting and that between the face of the bottom hole and drill bit matrix (i.e. the filled volume of the hole bottom) should be guaranteed. On this basis, the calculation formula for defining the penetration rate (footage per revolution) is presented. The formula shows the function of the penetration rate vs diamond exposure at drill bit face and degree of discharged cuttings. The concepts of normal and anomalous diamond exposure have been given. Laboratory and field production experiments have been performed on the diamond drill bits with normal and anomalous diamond exposure with positive results.