Carl Thaemlitz, Aramco Services Company
Welcome to SPE Drilling & Completion journal’s second issue of the 30th volume. This quarter’s edition presents us with drilling-focused papers related to the topics of transient-flow modeling, automated well control, drillstring dynamics, and fluid-friction factors. Completion-focused topics addressed include assessing the risks of high-density perforations, evaluating and interpreting casing wear, and particle-size distribution (PSD) concerns related to standalone screens. I hope that you find the readings to be informative, thought provoking, and enjoyable.
Transient-flow models play an important role in advanced well operations, such as managed pressure drilling and underbalanced operations. Flow models are often combined with control algorithms in operational settings for the purpose of controlling flow parameters. On the Advection-Upstream-Splitting-Model Hybrid Scheme: A Simple Transient-Flow Model for Managed-Pressure-Drilling and Underbalanced-Drilling Applications presents the capability of a model to handle highly changing flow scenarios through examples taken from managed pressure drilling (MPD) and underbalanced operations. The dynamic processes of mass transport and the propagation of rapid pressure waves are shown to be represented by the numerical capability of this advection upstream splitting model (AUSMV) scheme. On the basis of the simulation results, the scheme has demonstrated that it can handle highly dynamic-flow behaviors that are applicable to underbalanced-drilling (UBD) and MPD.
The detection and control of gas kicks in an oil-based mud while drilling through narrow pore-pressure/fracture-pressure windows has always been a challenge because of the gas solubility and mud compressibility. Automated Dynamic Well Control With Managed-Pressure Drilling: A Case Study and Simulation Analysis presents how continuous closed loop monitoring of the well, along with automated early kick detection and control, helps to keep the influx volume at a minimum before it reaches the well-control-threshold margin as outlined by the kick-tolerance matrix. Such early detection allows for significantly reduced nonproductive time by enabling influx circulation at full rate, thereby eliminating the need for flow check, blowout-preventer closure, and operational delays inherent in conventional well control. Consequently, the annulus pressures at the surface that are required to maintain constant bottomhole pressure can be kept at a practical minimum.
The investigation of oil well drillstring dynamics is essential for understanding the complex behavior of downhole vibration phenomena. Experimental test rigs allow for a reproduction of critical vibrations within a laboratory environment while at defined boundary conditions. A New Test Rig for Experimental Studies of Drillstring Vibrations presents a new scaled-rig for analyzing drillstring vibrations. The experimental system is capable of reproducing lateral drillstring vibrations with and without contact. This paper is focused on lateral vibrations of a bottomhole-assembly (BHA) section between two stabilizers. These oscillations are divided into four different states, which are no contact, forward whirl, backward whirl, and snaking. A review of existing test rigs is given.
Numerous fluids are pumped through various tubing geometries while under different conditions within the oil and gas industry. Frictional pressure loss calculations are of great importance in representing flow and the Darcy-Weisbach equation is routinely applied for this purpose. Frictional Pressure Losses of Fluids Flowing in Circular Conduits: A Review is an up-to-date critical review of the friction factor correlations. Discussions in detail on the methods of development, accuracy, applicability, and limitations for each correlation are presented. A pioneering algorithm, which can be used to develop a code for the prediction of friction factors, is offered to the industry. The algorithm is presented in a user friendly manner with the intention of helping personnel working in the oil and gas industry, without experience in the field of study, to calculate frictional pressure losses.
Evaluating the Risk of Casing Failure Caused by High-Density Perforation: A 3D Finite-Element-Method Study of Compaction-Induced Casing Deformation in a Deepwater Reservoir, Gulf of Mexico presents us with a new method to evaluate the feasibility of using a double-perforation approach in the completion of certain wells. In this paper, a 3D finite-element model is presented to determine the effect of the additional holes on casing failure. The model considers variations in both casing thickness and perforation pattern under expected wellbore and reservoir conditions. The finite-element model shows that casing deformation is not uniform, resulting from nonuniform strain loading across reservoir boundaries and nonuniform distribution of casing strength as a result of the perforation. The study quantifies how much casing strain to expect in the scenario described and the results suggest that models like the one described here offer a feasible method to assess casing deformation in highly compressible reservoirs, where high-density perforation may lead to casing failure.
Caliper logs provide valuable information in regard to the shape and wear of casing and tubing strings at various times throughout their operational life, and such information is often used to determine the remaining design strength. To clearly distinguish deformation and wear from the deviations caused by manufacturing tolerance, the caliper measurements can be compared with a baseline log run soon after a tubular string has been installed. However, a baseline log may not always be available. Assessing Casing Wear in the Absence of a Baseline Caliper Log addresses these situations and provides an assessment of what useful information can be obtained. A mathematical model is presented, along with complete numerical results from test cases on the basis of exact geometric shapes. Field examples are also included, along with implementation notes.
Our final paper, Particle-Size-Distribution Measurement Techniques and Their Relevance or Irrelevance to Wire-Wrap-Standalone-Screen Selection for Gradual-Formation-Failure Conditions, presents us with a critical review of the current practices in PSD determination. Preferred methods for the application of information obtained from PSD measurements, a proposed methodology toward determining what is relevant under gradual-formation-failure conditions for wire-wrap screens, and discussions of when such methodologies should be used and why, are all addressed. Experimental results that support the authors’ conclusions are also presented.