Unified Model for Gas-Liquid Pipe Flow Via Slug Dynamics: Part 1 — Model Development

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at different inclination angles from −90 to 90 deg. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

Stress Analysis of Composite Tubes Under Tensile Fatigue Loading in a Simulated Seawater Environment

It is the purpose of this study to investigate the effects of fatigue loading on two variations of hybrid composite tubes. The two types of samples are both composed of AS-4D/carbon fibers and e-glass fibers. The key distinctions between the two samples being the orientation and the number of layers. The samples were composed of the following orientations [90/20/90/20/90/20/20/90/20] and [90/90/20/90/20/20/90/20]. The experiment is designed to not only compare the two samples, but to develop some experimental data for a fatigue curve for similar materials. All loading for this experiment takes place in a controlled environment. Both temperature and the specific gravity of the water are measured and controlled.

VIV Predictions for an SCR in Sheared Ocean Currents

Vortex Induced Vibration (VIV) prediction is one of the key areas of interest in Deepwater Riser Engineering. Several Joint Industry Projects (JIPs) are currently in progress in this field, which results in an increase of experimental data available to design engineers, in revisions of specialized software and in development of new engineering tools. This paper presents VIV predictions for a hypothetical Steel Catenary Riser (SCR) using the latest versions of the SHEAR7 and the VIVA/VIVARRAY Programs. Both built-in and extended program capabilities are utilized and detailed plots of computation results are presented. Sensitivity studies on the influence of variations of selected design parameters are also included in the paper. Finite Element Analyses (FEAs) results and simple engineering tools were utilized in parallel to built-in program features. The calculations demonstrated, that for the riser investigated and presumably also for a wide variety of similar SCRs, that the built in program features are sufficient to predict VIVs conservatively. Notes on VIV predictions in a real ocean and on selected areas that require investigation are also included.

Experimental Evaluation of Control Fluid Fallback During Off-Bottom Well Control

This study measured the liquid fallback during simulated blowout conditions. The purpose of the study was to establish a basis for developing a procedure for controlling blowouts that relies on the accumulation of liquid kill fluid injected while the well continues to flow. The results from full-scale experiments performed with natural gas and water based drilling fluid in a vertical 2787-foot deep research well are presented. The results show that the critical velocity that prevents control fluid accumulation can be predicted by adapting Turner’s model of terminal velocity based on the liquid droplet theory to consider the flow conditions, velocity and properties of the continuous phase when determining the drag coefficient. Similarly, the amount of liquid that flows countercurrent into and accumulates in the well can be predicted based on the concept of zero net liquid flow (ZNLF) holdup.

Investigation of Drillstring Transverse Vibrations at Rotary Drilling of Inclined Wells

Significant part of axial compression load transferred to the bit while drilling of wells with high zenith angles is resisted by service drill pipes. By the action of static critical load, buckling of drillstring occurs initially in the shape of a sinusoid and subsequently, as the load increases, in the shape of a helix. Drillstring rotation promotes the occurrence of critical modes. As a result the drillstring can start snaking motion at the low side of the hole. When the rotary speed grows, whirling of the drillstring can occur with axial load much lower than the buckling load. In this paper, a nonlinear mathematical model of lateral vibrations of a rotating drillstring in straitened space of a straight inclined hole is proposed. A numerical method to solve drillstring motion equations has been developed that allowed to reduce time of computation. This made it possible to conduct a detailed study of how the main drilling parameters (compression load, drillstring rotary speed, hole angle, friction factor, etc.) effect drillstring motion in the well. Results of the study may be used to choose drillstring operation modes for rotary drilling of inclined and horizontal wells.

New Micromechanics Formulations for the Assessment of Elastic Moduli of Granular Assemblies

The elastic moduli of granular assemblies are sensitive to the confining conditions as well as the volume fractions of each of its constituents (i.e. solid, fluid, gas). Theoretical estimations using granular mechanics are based on assumed distributions of contact normals and branch vectors using idealized particle shapes and therefore cannot quantitatively predict the moduli. This paper presents a new method to use the moduli of the granular skeleton and those of the matrix to estimate the moduli of the composite and makes it possible to back-calculate the moduli of the skeleton from the moduli of the composite and the matrix.

Recent Advances in Barite Sag Technology

The occurrence of barite sag is a well recognized but poorly understood phenomenon in the drilling industry. Industry experts have offered a variety of measuring parameters, based upon empirical data, that only partially correlate with the occurrence of barite sag. The industry’s lack of understanding of the mechanisms and types of barite sag generally result in a poor correlation between laboratory results and field observations of barite sag. The financial impact of barite sag on drilling costs, usually resulting from rig-time lost while circulating and conditioning the mud system, is not trivial. There are reported incidences where recurring barite sag problems have resulted in the loss of drilling projects. The accuracy and relevance of technology utilized to manage barite sag can help reduce drilling costs. In the field barite sag frequently occurs in deviated wells where pipe eccentricity creates conditions conducive to dynamic sag. With the exception of a flow loop, laboratory tests do not simulate field conditions. Historically, laboratory tests characterize density variations arising from a vertical fluid column as static or dynamic sag without proper consideration to angle, pipe eccentricity, annular shear rates and annular flow. This paper reviews traditional and newly-emerging barite sag technology and compares their ability to predict barite sag potential. This potential will be determined under dynamic and static conditions in a sophisticated flow loop configured to match certain field conditions.

Protecting Proprietary Software in the Petroleum Industry

The development, management, and exploitation of Intellectual Property is critical to the health and prosperity of the Petroleum Industry. This paper provides a summary of how Petroleum companies can protect their proprietary software. Specifically, this paper will address the risks and benefits associated with protecting proprietary software through copyrights, patents, or trade secrets. With this background, the paper will address how Petroleum Companies can optimally develop, manage, and exploit their Intellectual Property to maximize industry production, efficiency, and profitability.

An Improved Approach to the Semi-Process-Oriented Implementation of Standardised ERP-Systems

The improved approach is considered as a life-cycle model that combines the necessities of process improvement projects and the implementation of modern integrated Standard Software systems. To improve the company’s business processes by means of the Standard Software implementation, each phase of the entire implementation life cycle puts its focus on optimising the customer’s underlying business processes. In addition, to intensify the benefits resulting from the process-oriented system implementation, the presented approach is extended by a certain guidance to organise a process-driven project team.

Using Torsion Bar Testing to Determine Fracture Toughness of Ceramic Materials

A new method, designated as Spiral Notch Torsion Test (SNoTT), is introduced for determining fracture toughness KIC of materials ranging from metallic alloys to brittle ceramics and their composites. A round-rod specimen having a V-grooved spiral line with a 45° pitch is subjected to pure torsion. This loading configuration creates a uniform tensile-stress crack-opening mode, Mode-I, with a transverse plane-strain state along the grooved line. This technique is analogous to the conventional test method using a compact-type specimen with a thickness equivalent to the full length of the spiral line. KIC values are determined from the fracture load and crack length with the aid of an in-house developed 3-D finite element program (TOR3D-KIC). A mixed mode (modes I and III) fracture toughness value can be determined by varying the pitch of the spiral line or varying the ratio of axial to torsion loads. Since the key information needed for determining KIC values is manifested within a small region near the crack tip, the specimen can be significantly miniaturized without the loss of generality. Limited results obtained for various materials are compared with published KIC values, showing differences of less than 2% in general and 6% maximum in one case. The experimental technique and theoretical basis of the proposed method are presented in detail.