Comprehensive Hydromechanical Specific Energy Calculation for Drilling Efficiency

Abstract

Over the last few years, different types of bits have been introduced to meet the chal lenges of steerable as well as rotary steerable systems; and it is imperative that bits be utilized optimally in these systems. Aw challenges increase with increasing depths, it becomes even more important for one to efficiently utilize the available energy (Robello, S., 2013, "Modeling and Analysis of Drillstring Vibration in Riserless Environment," ASME J. Energy Res. Technol., 135(1), p. 013101). A new correlation identifying ineffi cient drilling conditions is presented in this paper. Mechanical specific energy (MSE) has been used to improve drilling rates, with mixed results. Hydro MSE (HMSE), which is introduced here, encompasses hydraulic as well as mechanical energy. HMSE quantifies the amount of energy required to drill a unit volume of rock and remove it from under neath the bit. HMSE includes axial, torsional, and hydraulic energy and is different from MSE because it includes a hydraulic term. The initial MSE correlation (Teale, R., 1965, "The Concept of Specific Energy in Rock Drilling," Int. J. Rock Mech. Min. Sci., 2, pp. 57-73.) was modified to accommodate the new hydraulic term. This paper attempts to better model downhole drilling by introducing the hydraulic energy term in the MSE cor relation by defining it as HMSE. While the majority of the drilling occurs because of the bit, it is a well-known fact that some drilling occurs due to the "jet impact impingement" caused by the drilling fluid as well. Experimental and field data presented in this papershow that HMSE can identify inefficient drilling conditions. The new hydraulic term included in the specific energy correlation is the key to correctly match the amount of energy required to drill and overcome the strength and stresses of formation being drilled. Also, this new term illustrates how much hydraulic energy is needed to drill faster when the mechanical energy (axial and torsional) is increased. The results also show the importance of including the bit hydraulic energy term into any specific energy analysis for drilling optimization. Field results reveal specific patterns for inefficient drilling con ditions and also reveal a good correlation between calculated HMSE and the expected requirements for rock removal under existent conditions of stress at the bit face (Mohan,

A novel method for estimating the real-time dullness of tri-cone oil drill bits

“…Mohan et al [5] showed that the hydraulic energy has a great influence on drilling efficiency. The mechanical specific energy model was modified to include the effect hydraulic energy, but the developed MSE model is suitable for high pressure jet drilling and soft formation drilling.…”

“…The weight exerted on the bit is distributed on all cutters. Figure (5) shows how the exerted weight on bit is equal to the summation of the forces produced from the bit inserts or teeth [26].…”

Drilling Performance Optimization Based on Mechanical Specific Energy Technologies

“…Recently some researchers think that hydraulic energy also aids in actual drilling for certain formations, then they add the hydraulic term to the MSE function as [9,11].…”

“…The total mechanical work done by the bit in 1 h can be estimated as Please note that every bit has a mechanical efficiency for drilling when it is produced. The mechanical efficiency is mainly related to the bit's cutting structure and exists all along the drilling process [10,11]. Given the mechanical efficiency of the new bit, the mechanical work required to break the rock drilled in 1 h can be nearly expressed as…”

“…Then numerous investigators were motivated to develop more accurate models. These models include those presented by Pessier and Fear [7], Dupriest and Koeteritz [5], Armenta [8], Mohan et al [9], Cherif [10], Mohan et al [11] and they have been widely used in bit selection, drilling efficiency quantification, drilling performance monitoring, drilling performance optimization, ROP improvement and so on. Although the MSE obtained from these models are more and more precisely model the actual downhole drilling in vertical wells, currently there are few effective MSE models to precisely model the actual downhole drilling in directional or horizontal wells due to the majority of field data is in the form of surface measurements.…”