Exploitation of Field Drilling Data with an Innovative Drilling Simulator: Highly Effective Simulation of Rotating and Sliding Mode

Drilling challenging wells requires a combination of drilling analytics and comprehensive simulation to prevent poor drilling performance and avoid drilling issues for the upcoming drilling campaign. This work focuses on the capabilities of a drilling simulator that can simulate the directional drilling process with the use of actual field data for the training of students and professionals. This paper presents the results of simulating both rotating and sliding modes and successfully matching the rate of penetration and the trajectory of an S-type well. Monitored drilling data from the well were used to simulate the drilling process. These included weight on bit, revolutions per minute, flow rate, bit type, inclination and drilling fluid properties. The well was an S-type well with maximum inclination of 16 degrees. There were continuous variations from rotating to sliding mode, and the challenge was approached by classifying drilling data into intervals of 20 feet to obtain an appropriate resolution and efficient simulation. The simulator requires formation strength, pore and fracture pressures, and details of well lithology, thus simulating the actual drilling environment. The uniaxial compressive strength of the rock layer is calculated from p–wave velocity data from an offset field. Rock drillability is finally estimated as a function of the rock properties of the drilled layer, bit type and the values of the drilling parameters. It is then converted to rate of penetration and matched to actual data. Changes in the drilling parameters were followed as per the field data. The simulator reproduces the drilling process in real-time and allows the driller to make instantaneous changes to all drilling parameters. The simulator provides the rate of penetration, torque, standpipe pressure, and trajectory as output. This enables the user to have on-the-fly interference with the drilling process and allows him/her to modify any of the important drilling parameters. Thus, the user can determine the effect of such changes on the effectiveness of drilling, which can lead to effective drilling optimization. Certain intervals were investigated independently to give a more detailed analysis of the simulation outcome. Additional drilling data such as hook load and standpipe pressure were analyzed to determine and evaluate the drilling performance of a particular interval and to consider them in the optimization process. The resulting rate of penetration and well trajectory simulation results show an excellent match with field data. The simulation illustrates the continuous change between rotating and sliding mode as well as the accurate synchronous matching of the rate of penetration and trajectory. The results prove that the simulator is an excellent tool for students and professionals to simulate the drilling process prior to actual drilling of the next inclined well.

A new approach to evaluate rock drillability of polycrystalline diamond compact bits using scratch test data

Rock drillability is a comprehensive index that indicates the ease of drilling a hole in the rock mass, which is a main basis for the design of drilling bits, the optimization of drilling operational parameters, and the prediction of rate of penetration. This paper established a conversion relationship between mechanical specific energy measured from micro-drilling tests and mechanical specific energy measured from scratch tests, based on the consistency of rock breaking mechanism between these two types of tests. By incorporating the methodology of calculating rock drillability grade of polycrystalline diamond compact bits, a new mathematical model for predicting rock drillability of polycrystalline diamond compact bits is developed. Subsequently, a new method for acquiring continuous rock drillability profile by scratching the core surface is developed. A wide range of rocks with different hardness were tested by the proposed scratch method. The results show that the new model has high consistency with the results of laboratory micro-drilling tests. For example, the average errors of sandstone, shale, and carbonate test results are only 7.41%, 8.18%, and 4%, respectively. The new method can fully characterize the effect of mineral composition, cementation strength, and microstructure of rock on drillability. Besides, the new model has high utilization efficiency of expensive core samples because the core usually remains nondestructive after scratch tests.