An approach for modeling the field drilling data

It is well-known that even a small percentage of reduction in bit-related cost can result in significant savings. Improving bit performance is an effective approach to cost reduction and modeling bit performance is a scientific approach to optimizing of bit performance. However modeling bit performance has long been diminished, since to develop a model under experimental conditions is usually costly and few models from experimental or theoretical conditions have been practically utilizable. Following up the success in developing a practical method for modeling ROP using logging data from the North See area 1,2,3 , this paper explains the developed method further with a series of case studies including modeling ROP for a combination of bit runs, individual bit runs, short section under dynamic drilling conditions. The data were from 46 insert-tricone-bit-run of the 12-1/4 section of an onshore exploration well in Japan. The data were measured at surface with conventional logging equpment. The mud is water-based Lignosulphonate system and the formation is namely Hiuchiyama including variegated sequence of sedimentary and igneous rocks. The developed model succinctly explain about 80% of the ROP variations and the median of the normalized ROP residuals (NReROP) is around 10 to 15 %. The essence of the developed method is by grouping data to improve the suitability of data for modeling and still retain the information representing the intrinsic relations between the variables. The nature of the presented method are discussed and the utilizability and limitation of the models are addressed. Now that this method consistently appears to be physically valid and practically utilizable, it is intended for application in routine drilling practice in conjunction with further improvement and modification.