Improving oilfield performance enabling horizontal drilling techniques: developments and optimization of standard and special measures for a real case study

Abstract

Drilling technique is a crucial issue to pay attention to. Drilling a horizontal well has a great interest to the oil and gas industry since nowadays it provides attractive means for improving both production rate and yet the recovery efficiency. The great improvements in drilling technology make it possible to drill horizontally no matter how complex are the trajectories and how deep it is suppose to reach. This study aims at presenting the optimal design aspects of a horizontal well. Design aspects include the selection of bit and casing sizes, detection of setting depths and drilling fluid density, casing, hydraulics, well profile, and construction of drill string simulator. When many vertical wells exist, an oil field named (Z14 field) should be designated to have a short radius horizontal well able to increasing the productivity and to promote the developing of the field itself. A single build profile with build rate 90 deg/100ft is constructed based on geological data. A drill string simulator composed of soft-string model and buckling tendency is constructed to predict torque and drag of string for six operating conditions. These conditions are pick-up, slack-off, sliding, pick-up with rotation, slack-off with rotation and drilling with rotation. Results of loads analysis showed that the suggested drill string can be used without exceeding torsional, tensile and buckling strengths. Analysis of single build profile showed that the torque and drag while drilling horizontal well could be minimized by drilling with low build rate, employing lighter pipe, and improving the lubricating capability with oil base mud (low friction forces). A finite element model was constructed to predict inclination tendency for multistabilizer rotary BHA in three dimensions, static condition. The bottom hole assembly was idealized with beam element capable of resisting axial forces, bending moments about the two principal axes, and twisting moments about its centroidal axis. Bit and stabilizer were treated as contact point and restricted from movement in all directions. Each element is loaded with gravity and normal contact forces. Model validation showed closer agreement between the model and Jiazhi's method (analytic) for slick, single, and two stabilizers BHA, compared to Akgun results. Predictions with finite element model showed that for building assembly, the weight on bit had small effect on bit side force especially in high angle wells. Also inclination tendency (building, dropping) would depend on position of the stabilizer, diameter of drillcollar behind the bit, and number of stabilizers.