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Horizontal well drill string is simplified into a horizontal rotating beam, the beam–borehole interaction model and the bit–rock interaction model of horizontal well drilling string system are also analyzed. Based on the above analysis, the equations which describe the nonlinear dynamics of the mechanical system are derived by Timoshenko's beam model and extended Hamilton's principle. The system are analyzed in nonlinear dynamics based on the equations, the results show that: in the process of movement, horizontal beam is always in the lower right location of the wellbore; with the increase of weight on bit, radial amplitude of beam rises slightly, longitudinal amplitude of beam declines; with the increase of rotating speed, radial amplitude of beam rises, longitudinal amplitude of beam also rises. [ABSTRACT FROM AUTHOR]

Data-driven models can be used as an efficient proxy to model complex concepts in engineering. It is common engineering practice to optimize some controllable input parameters in a model to increase efficiency of operations. Machine Learning can be used to predict the rate of penetration (ROP) during drilling to a great accuracy as shown by Hegde, Wallace, and Gray (2015). This paper illustrates the use of machine learning to predict and increase ROP effectively. The machine learning model is first used to predict ROP – with input parameters such as weight on bit (WOB), rotations per minute of the drill bit (RPM), and flow rate of the drilling mud. The input parameters are then modified to increase ROP. This process has been applied to field drilling data from a vertical well consisting of different rocks and formations. The procedure can be used to determine the maximum achievable ROP in each formation, and map out operational guidelines for drilling of pad wells. A post drilling analysis can be conducted for pad wells to cut costs and save time while drilling. This model is very innovative because only surface measured parameters are used, without a priori requirements for geological, laboratory, or drilling data. [ABSTRACT FROM AUTHOR]

Wellbore instability is one of the most critical challenges that continuously appear in drilling and production operations. Borehole breakout, as the enlargement and elongation of a borehole in a preferential direction, is an important phenomenon which should be addressed when stability of the wellbore is analyzed. Breakout pressure is an important parameter in wellbore stability analysis. In this paper, a geomechanical model was constructed using several petrophysical, field and lab data for one formation of interest to evaluate in-situ and induced stresses. Three shear failure criteria, namely Mohr-Coulomb, Mogi-Coulomb and Hoek-Brown were used to predict the breakout pressure profile and the outcomes were validated with 4-arm caliper log data of the well. The effect of azimuth and inclination of the deviated wells on the breakout pressure was investigated using stress transformation equations. It was found that the Hoek-Brown failure criterion with optimized constants resulted in the best prediction of the breakout pressure for this particular case under study. As for the deviated wells, inclination had an increasing effect on the breakout pressure whereas azimuth relative to the maximum horizontal stress could counteract it. [ABSTRACT FROM AUTHOR]

In coalbed-methane (CBM) projects, conventional logs, such as density were used heavily for coal identification, coal-property derivation, and also potentially for coal ranking. This paper presents a novel work flow of density-log normalization for CBM wells. It addresses two major challenges to current normalization methods: absence of a pervasive reference layer and removal of geological effects after normalization. To overcome these disadvantages, the proposed work flow undertakes six steps, which are data quality control (QC), geological- area segmentation, subarea type-well selection, density-control points, variable linear transformation and normalized-log result QC with box plots, matrix crossplots, and several histograms. This work flow removes the systematic errors caused by acquiring logs at different times with different logging instruments provided by different vendors. Furthermore, it possesses the advantages of the automated QC work flow, type-well control, and reference-layer methods without incurring their respective disadvantages. It was applied successfully to approximately 600 wells covering a large area in the Surat basin of Australia. Proper log normalization will reduce the uncertainties involved in 3D geological modeling and will increase the accuracy of reservoir evaluation. This paper should therefore be of interest to petrophysicists and geologists involved in CBM-field characterization. [ABSTRACT FROM AUTHOR]

In this study, the health risk of toxic volatile organic compounds (VOCs) species for well drillers, working at an exposure site around a well of underground coal fire site, was presented in a case of Shanxi province. The samples were collected by Teflon sampling bags and measured by gas chromatography-mass spectrometry (GC-MS). The results showed that isopropyl alcohol was the most abundant compound of VOCs, with the geometric mean concentrations of 1700.38 μg/m. The geometric mean concentrations of individual BTEX compounds obtained in all of the sampling campaign were 131.64, 10.15, 15.53, and 25.38 μg/m for benzene, toluene, ethyl-benzene, and xylenes, respectively. Relative proportion of BTEX averaged as 8.5:0.7:1:1.6. High B/T ratio (13.0) and low T/E ratio (0.7) was observed in this study. For non-cancer risk in this study, the hazardous quotient (HQ) of 1,2-dibromoethane, 1,3-butadiene, and benzene was 17.91, 1.71, and 43.88, respectively, mean their non-cancer risk was at the level of definite concern. The HQ sum of 20 VOCs was 64.94, much higher than 1. The cancer risk values of benzene (7.01E-04), 1,2-dibromoethane (1.91E-04), carbon tetrachloride (1.55E-04), and 1,3-butadiene (1.09E-04) were greater than 10, indicating that they were all definite risk. The total cancer risk of all VOCs species was 1.39E-03, almost 14 times more than the level of definite risk. The stochastic exposure assessment of all VOCs species total cancer risk using the Monte Carlo simulation analysis shows that 5 and 95 % cancer risks were predicted to be 7.60E-04 and 2.75E-03, respectively. The cancer risk for all VOCs species is unacceptable. The results of sensitivity analysis show that benzene, carbon tetrachloride, and 1,3-butadiene exposure account for more than 98 % contributions to the estimated risk for drillers, indicating that those VOCs species exposure has greater impact than other species on risk assessment. Both combined effects and independent effects of each VOCs species have to be considered. [ABSTRACT FROM AUTHOR]

The drilling of salt formations generates particulate material composed of salt mixtures. In water-based muds (WBM) along the annular section, these salt mixtures tend to dissolve. The dissolution can cause changes to the drilling fluids. Its can lead to the well enlarging, to salt gravels accumulating at the bottom of the borehole, and other operational problems. The objective of this work is to study the dissolution of salt particles in brine and evaluate the mass transfer coefficient. The experimental data of the salt dissolved in brine along a flow system was obtained through an experimental apparatus consisting essentially of a mixer tank and a flow line. This study proposes a model based on the mass conservation equations for brine and solid salt particles. Samples of brine were taken along the flow system with the aim of evaluating the profiles of brine concentration versus position. The experiments were conducted for different operational conditions of brine flow and solid particles fed into the system. The experimental data were used as input for evaluating the overall coefficient of mass transfer. The system of partial differential equations (PDE׳s) was discretized in space by finite differences. The discretized model becomes a system of ordinary differential equation (ODE׳s) that can be solved using a subroutine LSODE in FORTRAN language. The hypothesis of steady state simplifies the model, allowing it to be solved analytically. The mathematical model is able to simulate the experimental data under different conditions, showing that the proposed model is capable of predicting experimental outputs under the studied range. The average deviation between the experimental values and the simulated values was less than 2.3%. [ABSTRACT FROM AUTHOR]

The distribution of some selected constructional and hydrogeological parametres of drilled wells located in the Małopolska province is analysed. The type of satistical distribution determined the measure of location calculation method (e.g. average value, median). In the case of normal distributions or similar (lognormal distribution), the average as a measure of location is recommended, while in the case of asymmetrical ones - the median. Preliminary analysis indicates that if we assess the total of 112 statistical distributions of the parametres examined, 5 cases (4.5% of all) are normal distributions, and in 95.5% of the cases we deal with asymmetrical distributions. The current study aims to present empirical distribution of the elements examined and to find the method of location measurement. [ABSTRACT FROM AUTHOR]

The article discusses the results and the process of the abrupt planning and execution of the first multilateral well in the Gulf of Thailand drilled and completed by Chevron International Ltd. It highlights on the good and bad aftermath scenarios of this project. Consequently, the said project is believed not to be considered as an economic success considering its significant cost incurred during the drilling process as well as other factors like its low oil rates. Furthermore, appropriate risk awareness and appropriate time of plan is perceived as two most important keys on the preparation of any projects.

A new type of rotary steering stabilizer used in a common rotary bottom hole assembly (BHA) to control well path was developed. In order for design and use of this kind of BHA, mathematical models were proposed for 3D mechanical analysis of rotary steering BHA with small deflection. The mathematical models include (1) differential equations; (2) boundary conditions of drill bit, stabilizer diameter change, tangent point, and bore hole wall; (3) methods for calculating lateral forces and deflection angles of the bit; and (4) models for determining navigation ability and navigation parameters. As an example, a given rotary steering BHA was studied. [ABSTRACT FROM AUTHOR]

The article discusses the field applications of a new brine-based, high density, solids-free cleaning fluids in balanced-displacements in deepwater and offshore shelf wells. The formation of the fluids were based on a recently discovered surfactant technology that was developed to ensure effective wellbore cleaning and design parameters as well as displacement modeling. A case history showed a reduction of more than 3, 000 psi with the new design from the expected 9, 000 psi from conventional water-based displacement. The formulation of high-density cleaning fluids, which has densities that can reach up to more than 17.5 ppg, proved to be successful through reduces differential pressure without compromising cleanup efficiency.

This study examines the determinants of health, safety, and environmental (HS&E) incidence and reporting behavior in Gulf of Mexico offshore drilling. One objective is to determine statistically significant variables that influence the probability of HS&E incidence and reporting. Incidence modeling employs standard qualitative response models with binary and ordered dependent variables, and a Poisson specification. A second objective is to examine the impact of imperfect reporting on inferences. Unlike previous studies, models allowing for the possibility of imperfect reporting are specified and estimated. The results of this analysis provide strong evidence to support the hypothesis that aspects of well complexity and site complexity increase the likelihood of HS&E incidents in drilling. Equally important is evidence rejecting the hypothesis that broader oil company attributes influence HS&E incidence. An analysis of reporting behavior provides mixed support for the hypothesis that well-known firms are more likely to report an incident than their more anonymous counterparts. There is weak evidence indicating differential reporting behavior between regulatory districts. Finally, the analysis provides consistent support for the conclusion that a 1996 policy change reduced HS&E incidence and increased HS&E reporting. The results of this research provide guidance to company managers and regulators on the factors driving HS&E incidence and reporting. Results also provide evidence that models of imperfect reporting can alter, in this case reverse, the interpretation of trends in reported incidents. These results can be used to support efficient resource allocation to prevention efforts, and inform regulatory policy. [ABSTRACT FROM AUTHOR]

The article describes improvements made to the existing procedures of the American Petroleum Institute (API) RP13D standard practice on rheology and hydraulics, and provides an illustration of how these methods can be applied to complex well designs. It serves to present the industry to a modernized API standard, which offers an ideal foundation to inform new engineers of the fundamental concepts of hydraulic design and optimization. In addition, it presents project planning and management methods employed to complete the new document to meet an aggressive time line.

The article reports that the California Senate has passed the groundwater data bill SB 20 by a vote of 21-15 on June 1, 2015 which requires public access to the information on groundwater filed by well drillers file with the state's Department of Water Resources.