Current API RP13D guidelines outline 3 methods for determining hole-cleaning efficiency based on wellbore angle. Method 1, used in low-angle wellbores (<30°) compares cuttings slip velocity with annular velocity to determine a transport ratio and cuttings concentration. Method 2, also used for low-angle wellbores (<30°) derives a carrying capacity index (CCI) based on bulk annular velocity, fluid density and power-law rheology. Method 3, used in high-angle wellbores (<30°) derives a transport index (TI) based on fluid rheology, density, and flow rate. TI is then plotted on an empirically derived chart (Luo et al., 1992, 1994) to determine maximum allowable rate of penetration (ROP) that should ensure efficient hole cleaning. Although these methods are considered recommended practices by API, Method 3 (TI) is based on an outdated study (Luo et al., 1992) with limited scope (one flow loop, one field test). Additionally, this method neglects the importance of drill pipe rotation and pipe eccentricity in cuttings transport efficiency, which has been proven to be a factor in other studies (Akhshik et al., 2015; Sanchez et al., 1997b). This paper highlights the shortcomings of current API standards and identifies what effects contributing factors such as pipe eccentricity and drill pipe rotation rates may have on cuttings transport efficiency. Further, this paper discusses the impact pipe-to-hole area ratio and wellbore flow area have on the effects of drill pipe rotation and flow channeling. Five horizontal wellbores were modeled using Siemens Star CCM+ Computational Fluid Dynamics (CFD) software, with bottom-eccentric 4 ½″ drill pipe placement, in annular diameters of 6¾″, 7 ⅞″, 8 ⅜″ 8 ½″ and 8 ⅝″. Additionally, one bottom-eccentric 5″ drill pipe in an 8 ¾" wellbore was modeled to compare identical pipe-to-hole area ratios with different flow areas. Simulations were run with drill pipe rotation speeds increasing from 0 to 180 RPM, in 30 RPM increments. In order to determine the impact fluid rheology has on flow channel development, both medium density oil-based muds and light density water-based muds were modeled and compared. Bulk annular flow velocity was set to 100 ft/min, to maximize the observable effects of drill pipe rotation. Bulk average velocity was calculated from cross sectional area, determining both annular velocity (velocity parallel to wellbore) and absolute velocity (fluid velocity magnitude regardless of direction). The resultant velocity profiles were used as the annular velocity component in API CCI and TI calculations and compared to bulk annular velocity. In addition to observing fluid velocity for CCI and TI calculations, changes in effective viscosity from the onset of pipe rotation was also analyzed to determine changes in wellbore parameters that may affect cuttings transport.

The main functions of heavy-duty lubricating-oil additives are to control engine fouling, bearing corrosion, and wear of liners and piston rings. Alkalinity is desirable for the control of wear and is one of the major requirements for the avoidance of piston fouling when conventional organo-metallic additives are used. In a well-balanced oil, sufficient dispersive power and oxidation stability may be incorporated to ensure adequate piston cleanliness and freedom from bearing corrosion provided that the alkalinity level is satisfactory. The alkalinity level falls during service, and for satisfactory performance with certain types of additive in common use it must be kept above a minimum value. For these additives equations are given which enable the variation of the alkalinity level with time in given circumstances to be predicted approximately. The most satisfactory arrangement is to use an oil containing sufficient alkalinity so that the concentration never falls below the critical value. The oil-change period is then determined by other considerations, for example, contamination with abrasives. If an oil of lower alkalinity-concentration is used, then the equations developed permit an approximate estimate of the oil-change period, determined solely from the aspect of additive effectiveness. The application of these results to engines with separate cylinder lubrication is discussed. Thus oils, and, where appropriate, oil-change periods, may be selected on a rational basis instead of by trial and error.

In recent years, an industry-wide demand for increased drilling efficiency has led to the development of technologies and methods focused on multi-well pad development and the minimization of the transportation of drilling rigs between locations. Studies have indicated the potential for improving drilling cycle efficiency through improvements in rig design and procedural documentation but have given limited consideration to the unitization and mobilization practices surrounding ancillary components such as mud pumps, light plants, bulk fluid storage and other systems that comprise modern land rigs. This study examines current unitization practices, as well as offers alternative methods of integrating ancillary system components to improve current transport configurations. Specifically, ancillary systems whose transport dimensions and weight exceed the federal and state requirements for commercial vehicles operating within the National Highway Freight Network (NHFN). In this study, the application of transport logistics software is used to demonstrate that there exists the potential for significant reduction in land rig mobilization costs through revised unitization of drilling rig ancillary systems. Permit data from proposed wells located in the Permian, Bakken, and Marcellus are utilized to develop transport scenarios whose focus is to quantify the impact of ancillary system unitization on the total fee structure associated with rig mobilization between geographical regions. Within each scenario, ancillary systems from currently active rigs are compiled and itemized according to their weight, transport dimensions, and degree of component unitization. The resulting schedule is then processed through transport logistics software to identify fee schedules associated with oversize permits, overweight permits, civilian and police escorts, driver rate/fuel costs, and associated service fees for the individual loads. Following the conclusions derived from the analysis of the existing rig systems, the series of transport scenarios are repeated using revised component configurations. The revised system employs a combination of divisible and non-divisible loads whose components are either integrated as part of dedicated transport trailers or located within ISO containers loaded onto commercially available transport trailers. The fee schedules from active rigs, as well as the results from the proposed unitization, are explored in detail to identify critical areas for improvement regarding unitization practices for active rigs and future builds.

SummaryFollowing a brief discussion of various methods of measuring combustion efficiency in gas turbine chambers, the superiority in accuracy of applied gas analysis is stated. Factors leading to inefficiencies in combustion are outlined and the exhaust constituents requiring measurement are deduced. The chief difficulty in the past in the application of gas analysis methods to combustion efficiency determination has been the time consumed in actual analysis of samples; at Thornton Research Centre means of overcoming this difficulty have been investigated and several rapid and accurate analytical techniques have been developed and used successfully. These techniques are described, together with other promising methods at present under development. The broad requirements of obtaining exhaust gas samples for analysis are discussed and typical sampling systems described; precautions necessary in applying these systems are given. Formulse for the calculation of combustion efficiency from analytical results, together with any assumptions made, are given in the text and their derivation explained in an Appendix. The techniques described have been developed primarily for use in conjunction with rig testing of aircraft gas turbine combustion chambers; the broader application—for instance, to engine testing—of the principles involved are considered briefly.

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