Build-up Sections Research Articles

Prospective expertise: The use of ‘listen’ in the discourse of television sports pundits

This article details the functions of the imperative verb ‘listen’ in the pre-match build-up discussions of television football pundits. Data were recorded from live coverage of recent national and international football competitions. The analysis shows how ‘listen’ plays a role in what is referred to as prospective expertise: the work accomplished during the extensive pre-game build-up sections of a show, in which pundits engage in highlighting potential points of drama or sporting adversity to be anticipated in the game that is yet to be played. Three patterns are identified, in which different sequential positionings of ‘listen’ yield differing kinds of statements or evaluations, assessments, predictions and caveats regarding the forthcoming game.

Analysis and Research on Borehole Shrinkage Mechanisms and Their Control in Directional Wells in Deep Composite Salt Formations

Abstract The composite salt formations in West China are characterized by the deep burial, complex tectonic stress, and alternating development of salt rock and mudstone, and salt rock creep during drilling poses great challenges to the safety of drilling. This research is aimed at the serious blockage and sticking in build-up sections in deep composite salt formations. A 2D mechanical model for inclined wells penetrating multiple vertical layers was established by combining the analysis of creep mechanisms of composite salt formations with the high-temperature creep experiment results so as to investigate the wellbore stability of directional wells in composite salt formations in a certain block from the perspective of rock mechanics and probe the influence of inclination angles on borehole shrinkage under different in situ stress and interlayer conditions. Moreover, a directional well in the block was taken as an example to analyze the creep and borehole shrinkage in composite salt formations. The method for wellbore stability control was proposed, and the drilling fluid density chart was established. This research reveals the relationship among the wellbore trajectory, the degree of borehole shrinkage, and drilling fluid density in build-up sections of directional wells in composite salt formations and provides a theoretical reference for the establishment of the method for controlling blockage and sticking accidents in directional wells.

Analyzing of Drill Stem Test (DST) Result for Dual Porosity Limestone Reservoir

The aim of this paper is to discuss and evaluate the result of DST which was conducted in a limestone reservoir of an oil field at the depth interval 3764.29-3903.0 meter in well-1 to evaluate the dynamic characteristics of the reservoirs, for instance: skin effect, permeability, wellbore storage, reservoir boundary and average reservoir pressure. Reservoir Pressure profiles has been recorded for both Buildup and draw down intervals. Semi-log and log-log coordinates have been used to plot the pressure signature date of both buildup period and its derivative to improve diagnostic and Horner plot. In addition, a dual porosity reservoir and infinite acting characteristic was discovered as a result of the well test data interpretation. Wellbore storage, skin factor and transient flow effects have been detected in the DST analysis on the dual porosity behavior due to phase re distribution. Using final buildup sections, the flow parameters of dual porosity reservoir were determined as the flow between fissure and matrix was (7.558 x 10-6) while, the storability ratio between fissure and matrix was calculated as 0.3 and permeability is 102 MD for both matrix and the fissure together. However, negative value of skin factor mostly appears in double porosity limestone reservoirs, positive skin factor of the reservoir has been observed in this study. It can be considered that the positive skin factor can be resulted in either the formation was partially penetrated and /or wells were not cleaned up properly.

A magnet ranging calculation method for steerable drilling in build-up sections of twin parallel horizontal wells

In drilling technology, adequate control over the distance between adjacent sections of twin parallel horizontal wells has a significant impact on the final recovery rate from unconventional oil and gas resources, such as heavy oil and natural gas hydrates. For this distance to meet design requirements and to reduce the duration of the drilling period, it is necessary to use a rotating magnet ranging system that helps drill an injection well starting from the build-up section. Usually, the build-up sections of the twin parallel horizontal wells are not parallel. Therefore, the spatial relationship between the build-up sections of the two wells can be divided into two types, namely, converging coplanar and non-coplanar. In this paper, we propose a method based on an algorithm for finding extreme values to calculate the radial distance between the build-up sections of the twin parallel horizontal wells. In addition, we propose and discuss a method for calculation of the direction between the magnetic sub and the probe tube in the build-up sections using coordinate transformations combined with the rotating magnet ranging calculation for the horizontal sections of twin parallel horizontal wells. The simulation results indicate that the magnet ranging algorithm for the build-up sections of twin parallel horizontal wells has a precision of a few percent and can meet the actual needs of the drilling site.

Analysis of the External Pressure on Casings Induced by Salt-Gypsum Creep in Build-up Sections for Horizontal Wells

To alleviate the problems of casing collapse induced by the coupling effect of salt creep movement, as it relates to the curved sections of horizontal wells, an experimental approach was taken to determine the creep (visco-elastic) property of the salt-gypsum formation, using finite-difference software to establish a creep model with curved casing, wellbore and salt formation. With this model, the effects of borehole curvature, drilling direction and casing thickness on external pressure on casing were analyzed, and casing deformation in the non-uniform in situ stress field was simulated. For horizontal wells drilled through salt-gypsum formations, this analysis led to the following conclusions: (1) the casing tends to be much safer when drilling is undertaken along the direction of the minimum horizontal stress; (2) casing deformation occurs and stress increases as the borehole curvature increases; (3) for the same curvature and drilling direction, thicker casings are safer; (4) as the creep time increases, the external pressure on the casing rapidly increases until it reaches its maximum value, whereupon it stays at that value; (5) under the effect of non-uniform in situ stress, a larger non-uniform coefficient would result in greater external pressure on the casing. This model has been successfully applied to analyze the external pressure on curved casings in a build-up section for horizontal wells drilled through salt-gypsum formations in an oilfield in Northwest China. The model has helped to improve the casing design and reduce drilling downtime with greater wellbore stability in salt-gypsum formations.

A Comprehensive Modeling Analysis of Borehole Stability and Production-Liner Deformation for Inclined/Horizontal Wells Completed in a Highly Compacting Chalk Formation

Summary Numerous casing and production-liner deformation/failure problems have been reported in high-porosity chalk formations in both the overburden and the reservoir sections, causing costly operation problems that prevent workovers and recompletions. This paper presents the results of studies performed to investigate stability of an openhole, cemented liner and uncemented-liner completions in a highly compacting chalk formation. The effects of critical cavity dimensions caused by various acid-stimulation techniques were also investigated. On the basis of the review of historical caliper-survey data, we ascertain that axial-compression collapse is a major liner-deformation mechanism in the reservoir zones. Axial-compression collapse has been found in both low-angle wells (also in buildup sections of horizontal wells) and horizontal laterals. The casing deformation in low-angle sections is a result of reservoir compaction (i.e., change in the vertical formation strain), while the deformation in horizontal sections is primarily induced by increased axial loading because of cavity deformation. The current completion practice using cluster perforations and high-volume acid treatments causes vertically enlarged cavities, resulting in poor radial constraint. A series of laboratory triaxial tests was performed on selected reservoir chalk samples to measure the stress/strain and failure behavior of the chalk formation considering a wide range of porosity and water saturation and different levels of confining pressures. Using the chalk-failure criteria and constitutive relations developed from the analysis of laboratory triaxial-compression-test data, a 3D nonlinear poroelastic/plastic finite-element-method (FEM) model was developed for the openhole stability analysis. The simulation results show that the abnormally high ductility of chalks after pore collapse around a borehole could actually enhance borehole stability, with a magnitude beyond expectation. In this study, analytical and numerical models are also developed for evaluating cavity-induced axial-compression collapse of production liners. Model results indicate that the risk of the cavity-induced axial-compression collapse substantially increases for short perforated intervals stimulated with large acid treatments. However, increasing the perforation-interval lengths along the entire liner axis results in more-uniform acid distribution and will greatly reduce the chance of axial-compression collapse caused by localized cavity deformation. On the basis of these analysis results, key completion design criteria and stimulation strategies were developed for wells completed in highly compacting chalk reservoirs to reduce risk of casing and liner mechanical problems.

A New Method To Predict Performance of Horizontal and Multilateral Wells

Summary Production enhancement and ultimate recovery improvement have given horizontal wells the edge over vertical wells in many marginal reservoirs. However, it is more expensive to drill and complete a horizontal well than a vertical one. Therefore, to determine the economical feasibility of drilling a horizontal well, engineers need reliable methods to estimate its productivity. After a broad literature review, a simple semianalytical model has been developed in this study for predicting the productivity of horizontal oil wells. This model couples flow from a box-shaped drainage volume to flow in the wellbore. Along with friction, acceleration, and fluid-inflow effect, change in flow regime from laminar to turbulent is also taken into account to describe flow in the wellbore. The reservoir-inflow model used in this productivity model represents flow in the reservoir using a combination of 1D and 2D models and also considers varying skin along the wellbore to account for the heterogeneity of the near-wellbore region because of drilling-fluid invasion into the formation. In addition, reservoir-permeability anisotropy and convergence of flow to the wellbore have been taken into account in this inflow model. Comparison of this model with three existing models using field data reveals that the proposed model is more accurate because of more-realistic modeling of reservoir inflow and wellbore flow. The semianalytical nature of this coupling model makes it comprehensive and applicable to reservoirs with varying conditions, especially heterogeneous reservoirs. Moreover, this productivity model can be extended easily to estimate the deliverability of multilateral wells by coupling the inflow performance of individual laterals with hydraulics in buildup sections and the main vertical section. A logical procedure for calculating the deliverability of multilateral wells by using this productivity model is described in this paper.

Effect of mid-connection detail on the behavior of x-bracing systems

In this paper, the effect of mid-connection detail of x-bracings comprised of build-up sections on the elastic–plastic behavior of braced systems is investigated. Then, a proposed symmetric mid-connection detail is compared with the commonly used one, analytically. In common mid-connection detail for build-up sections, one diagonal member (which is comprised of a pair of channels or angles) is usually discontinuous at the mid-connection and the other continuously passes through the connection. A rectangular gusset plate is used to join the discontinuous and continuous diagonals in practice. In the proposed method, one section from each diagonal member is discontinuous and the other is continuous. Buckling and post-buckling behavior of single span and single story models of cross-braced systems have been verified during a nonlinear static finite element analysis. The results show that the proposed mid-connection detail can improve both strength and ductility of cross-braced systems. Also, it is shown that adding two cover plates on both sides of discontinuous diagonal members in common mid-connection detail can partially improve the overall behavior of the system.

Design of oil wells using analytical friction models

Recent wells have been drilled to more than 10 km from the platform, and companies are planning to extend these beyond 12 km. Well friction is one of the most important limiting factors in this process. Torque and drag prognoses are developed today on in-house simulators. Although this is a good tool for planning, improvements are made on a trial and error basis, and these simulators have limited availability. To provide more insight into the frictional aspect, a larger study was undertaken. Explicit analytical equations are derived to model drill string tension for hoisting or lowering of the drill string. The equations are developed for straight sections, build-up sections, drop-off sections and side bends. Both constant curvature models and a new modified catenary model are derived. The new catenary model is developed for arbitrary entry and exit inclinations. Equations to determine well friction in three-dimensional well profiles are also given. In addition, expressions for torque and drag are developed based on the tension equations. Equations for combined motion and drilling with a motor are also given. Using these equations, the total friction in a well is derived from the sum of the contributions from each hole section. Examples are provided to demonstrate the application for ordinary production wells, catenary wells, long-reach wells and horizontal wells. Optimization criteria are developed to design the well for minimum friction.