J. Energy Resour. Technol. 1999;122(1):1-7. doi:10.1115/1.483154.

Percussion drilling technology was considered many years ago as one of the best approaches for hard rock drilling. Unfortunately, the efficiency of most hydraulic hammer (HH) designs was very low (8 percent maximum), so they were successfully used in shallow boreholes only. Thirty years of research and field drilling experience with HH application in former Soviet Union (FSU) countries led to the development of a new generation of HH designs with a proven efficiency of 40 percent. That advance achieved good operational results in hard rock at depths up to 2000 m and more. The most recent research has shown that there are opportunities to increase HH efficiency up to 70 percent. This paper presents HH basic design principles and operational features. The advantages of HH technology for coiled-tubing drilling is shown on the basis of test results recently conducted in the USA. [S0195-0738(00)00101-1]

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2000;122(1):14-21. doi:10.1115/1.483156.

The continuity and momentum equations for fully developed and spatially developing slug flows are established by considering the entire film zone as the control volume. They are used for the calculations of pressure gradient, slug frequency, liquid holdup in the film, flow pattern transition, slug dissipation, and slug tracking. Comparison with available experimental results shows that these equations correctly describe the slug dynamics in gas-liquid pipe flow. [S0195-0738(00)00701-9]

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2000;122(1):22-28. doi:10.1115/1.483157.

A new unified model is proposed for the transition from annular to intermittent flow patterns for the entire range of pipe inclination angles. Experimentally, it has been observed that the transition from annular flow takes place at a critical void fraction. To obtain a transition boundary equation, conservation of momentum equations for gas and the liquid film are combined and solved with the critical void fraction. The new model captures the correct transition characteristics, agrees favorably with experimental flow pattern data, and performs the best when compared with previous transition models. [S0195-0738(00)00601-4]

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1999;122(1):29-33. doi:10.1115/1.483158.

Sand production may be inevitable in many fields that have a relatively low formation strength. Sand erosion and settling predictions and sand monitoring are important elements of any effective sand production management strategy. Sand erosion predictions are used to establish tolerable sand production rates, and, thus, well productivity, and to develop cost-effective inspection frequency for critical components. Prediction of critical flow rate to prevent sand settling is important for flowlines that are not designed for pigging. Quantitative sand monitoring is essential in verifying the effectiveness of sand control procedures and in generating an important input parameter for erosion and sand settling predictions. This paper presents equations for predicting sand erosion rate and sand settling flow rate, and assesses the accuracy of these equations. In addition, the paper presents an assessment of the sensitivity of commercially available nonintrusive acoustic and intrusive electrical resistance sand monitors. [S0195-0738(00)00201-6]

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1999;122(1):34-41. doi:10.1115/1.483159.

The modeling of pressure transient across constrictions is achieved by using a one-dimensional, isothermal, noncompositional, single-phase representation of the Eulerian model. A TVD scheme was used to solve the ensuing nonhomogeneous hyperbolic set of first-order quasi-linear partial differential equations. Three types of constrictions were modeled and in each case the behavior of the transient was analyzed. This analysis was used to interpret the pressure response at the inlet resulting from the reflection of the transient at the constrictions. The comparisons between the predicted and inputted data are very good, suggesting that the technique has much promise. [S0195-0738(00)00301-0]

Topics: Pressure , Fluids , Pipes
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2000;122(1):42-47. doi:10.1115/1.483160.

The remote, diverless, simultaneous connection of multiple subsea flowlines has historically been a difficult and costly operation. Difficulties and intensified operational activities stem from the need to orient the multiple flow paths prior to the final connection of the tubulars. This rotational orientation has proven to be very difficult for randomly prelaid flowlines or flowlines which must be rotated a relatively large amount prior to makeup. A new, innovative method has been developed whereby multiple flowlines can be connected without the need to rotationally orient the multiple tubulars. This new connection system technology has undergone full-scale subsea testing and will be implemented in a major development in the North Sea. The significance of this achievement is assessed in this paper with a focus on the design philosophies used, the principles of operation, the overall system reliability, the projected amount of operational cost reduction, and the full-scale testing results. Additional comments are made concerning the applicability of this technology in various other subsea applications. [S0195-0738(00)00501-X]

Commentary by Dr. Valentin Fuster

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