BHA Selection and Parameter Definition Using Vibration Prediction Software Leads to Significant Drilling Performance Improvements

Abstract

The understanding and mitigation of downhole vibration has been the subject of intense scientific research in the drilling industry in recent years, as inefficient drilling results in slower and more expensive operations. In order to drill ahead, a sufficient amount of energy must be supplied by the rig to overcome the rock strength, the reactive torque of the drilling system, drag forces, fluid pressure losses, as well as the energy lost by way of downhole vibrations. It has been well documented that downhole vibrations are a significant drain on the amount of effective drilling energy available to the bit. When the drill string enters resonant modes of vibration, not only does the drilling efficiency decrease, but the likelihood of catastrophic drill string component failures increase. The amount of destructive energy expended in these resonant modes of vibration, when left unchecked, may overcome the material limits of components in the drill string. In this sense, the mitigation of downhole vibrations will result in faster, smoother, and cheaper drilling operations. Software using Finite Element Analysis (FEA) has been developed to understand these vibration phenomena and to predict which combinations of drilling parameters should result in more efficient drilling. The software graphically presents the results, depicting undesired levels of resonant vibration produced with specific drilling parameter combinations, based on the BHA geometry and wellbore design. Predictions made by this software have produced notable results, including a world record for Rate of Penetration (ROP) in the Gulf of Mexico. This paper also examines different Bottom Hole Assembly (BHA) designs and the resonant vibration modes that may be initiated while drilling, using the proprietary software package. The combination of proper BHA design and the correct selection of parameters results an overall improvement to drilling efficiency. A variety of case studies from Latin America, incorporating the results of the vibration analysis, will demonstrate solid improvements to drilling operations in terms of time and cost savings, increased penetration rates, and improved dull conditions. The use of field validated software for vibration prediction and mitigation has a potential role in the drilling industry as important as the introduction of PDC bits in the 1980s.

New Industry Standards to Increase the Reliability of Drilling Operations

“…If 100% of efficiency were achieved while drilling, the Mechanical Specific Energy (psi) or MSE (Teale, 1965) would be equal to the formation hardness (psi). Drill string dynamics alter as new joints of pipe are added, with a progressive increase in resonance modes that reduce the efficiency of the drilling operation (Amorim Jr., et al, 2012).…”

Dynamic Analysis of Bottom Hole Assembly With External Vibrating Force Excitation

“…And T,. 1 • is the torque given by t he rotary where Ec and Gc are elasticity and shear modulus of t he drill colla r, Dco is the outer diameter of the drill collar , l is the element length, .6.z and .6.¢ are t he axia l displacement difference and torsional rotation differen ce between t he two en ds of each element.…”

Drilling Assembly Vibration Model Validated with Frequency Domain Examination of Distributed Downhole Measurements

“…c c c  Resonance in drilling systems has been demonstrated in the past with measured downhole dynamics data, where the resonance manifested as elevated levels of axial, lateral, or torsional vibration. This was observed when the drilling system operated with the input drilling parameters that aligned with the natural frequencies of the system (Craig et al 2009;Amorim et al 2012;Teasdale et al 2012).…”