John Rogers Smith

Improved Bottomhole Pressure Control for Underbalanced Drilling Operations

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ResGrid: A Grid-aware Toolkit for Reservoir Uncertainty Analysis

Many efforts in Grid communities have focused on middleware research and development. However, Grid application-level tools are needed which can build higherlevel functionality on top of core middleware services. We work with specific classes of scientific applications and present a Grid-aware toolkit ResGrid for reservoir uncertainty analysis. With the help of the ResGrid, a reservoir engineer can transparently take advantage of Grid resources and services for compute-intensive and dataintensive uncertainty analysis as well as enforce the understanding of reservoir modeling. In this paper, the ResGrid is introduced in terms of overview, architecture, and implementation status.

A New Comprehensive, Mechanistic Model for Underbalanced Drilling Improves Wellbore Pressure Prediction.

A new comprehensive, mechanistic model that allows more precise predictions of wellbore pressure and two-phase flow parameters for underbalanced drilling (UBD) is proposed. The model incorporates the effects of fluid properties and pipe sizes and, thus, is largely free of the limitations of empirically based correlations. The model is validated against actual UBD field data and full-scale experiments in which the gas and liquid injection flow rates as well as drilling fluid properties were similar to those used in common UBD operations. Additionally, a comparison against two different commercial, empirically based UBD simulators shows better performance with the mechanistic model. Introduction It is generally accepted that the success of UBD operations is dependent on maintaining the wellbore pressure between the boundaries determined by formation pressure, wellbore stability, and the surface equipments flow capacity. Therefore, the ability to accurately predict wellbore pressure is critically important for both designing the UBD operation and predicting the effect of changes in the actual operation. Because of the complex nature of the hydraulic system of UBD operations in which two or more phases (liquid, gas, and solids) commonly flow, the prediction of pressure drop and flow parameters, such as liquid holdup and in-situ liquid and gas velocities, are performed mainly with empirical, two-phase flow methods. The Beggs and Brill 1 correlation is the most popular among the current, commercial UBD simulators. However, it is recognized by the petroleum industry that most of these empirical correlations were developed from experimental databases, thereby making extrapolation hazardous. 2 Moreover, the Beggs and Brill 1 correlation has been shown to overpredict or fail to predict bottomhole pressures for both vertical and horizontal UBD operations. 3 , 4 Since the mid-1970s, significant progress has been made in understanding the physics of two-phase flow in pipes and production systems. This progress has resulted in several two-phase flow mechanistic models to simulate pipelines and wells under steady-state as well as transient conditions. Consequently, mechanistic models, rather than empirical correlations, are being used with increasing frequency for designing multiphase production systems. Based on this trend of improvement, the application of mechanistic models to predict wellbore pressure and two-phase flow parameters seems to be the solution to increasing the success of UBD operations by improving such predictions.

Analysis of Alternative Well-Control Methods for Dual-Density Deepwater Drilling

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Diagnosis of Ineffective Drilling Using Cation Exchange Capacity of Shaly Formations

Shale and shaly formations are the most common lithologies encountered in drilling for oil and gas in the Gulf of Mexico. These formations often cause bit performance problem. This paper introduces a method relating bit performance to the cation exchange capacity of the shaly formation being drilled. The relationship between drilling parameters, such as normalized rate of penetration and specific energy, and cation exchange capacity is investigated statistically using actual field data. The correlations have shown potential for diagnosis of ineffective drilling of PDC bits in overpressured shaly formations. Template charts are developed based on the correlations to be used for the diagnosis of ineffective drilling for PDC bits while drilling over-pressured Miocens shales with water-based mud in offset wells.

Counter-Current and Co-Current Gas Kicks in “Horizontal” Wells: Non-Newtonian Rheology Effects

Results from experiments conducted in downward liquid-gas flows in inclined, eccentric annular pipes, with water-air and water-polymer-air mixtures as the working fluids, are presented. The gas was injected near the middle of the test-section length. This flow is directly relevant to what is found in down-grade portions of horizontal wells. Flow maps, in terms of liquid and gas superficial velocities, indicating the transitions between counter-current and co-current gas flows have been determined experimentally for four dip angles. The counter-current gas flow observed was always in the slug regime while the co-current one appeared as stratified. Counter-current flow fraction and void fraction measurements were carried out at various liquid superficial velocities and gas-injection rates and correlated to visual observations through a full-scale transparent test section. Results indicate that increase of the liquid yield point favors the development of counter current flow which is shown to occur at representative liquid superficial velocities and gas injection rates. Thus, counter-current flow can be easily generated at small downward dip angles, within the practical range of liquid superficial velocity for drilling operations, especially at low gas-injection rates.

Cement Pulsation Treatment in Wells

Cement pulsation is a novel technology for enhanced frequency, hydraulic pressure pulses to the wellhead. Data are presented from over 80 wells in drilling and after cementing.

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.Copyright

Co-Current and Countercurrent Migration of Gas Kicks in “Horizontal” Wells

Results from experiments conducted in downward liquid-gas flows in inclined, eccentric annular pipes, with water and air as the working fluids, are presented. The gas was injected in the middle of the test section length. The operating window, in terms of liquid and gas superficial velocities, within which countercurrent gas flow occurs at two low-dip angles, has been determined experimentally. The countercurrent flow observed was in the slug regime, while the co-current one was stratified. Countercurrent flow fraction and void fraction measurements were carried out at various liquid superficial velocities and gas injection rates and correlated to visual observations through a full-scale transparent test section. Our results indicate that countercurrent flow can be easily generated at small downward dip angles, within the practical range of liquid superficial velocity for drilling operations. Such flow is also favored by low gas injection rates.

A Study of Hydrocarbon Releases in the Gulf of Mexico, 1996 Thru 2010

The events surrounding the Deepwater Horizon (Macondo) disaster have changed the face of deepwater operations. Safety and environmental systems (SEMS) plans and capping or containment capabilities are required to meet current Bureau of Safety and Environmental Enforcement (BSEE) permitting requirements for the Gulf of Mexico (GOM). More generally, industry must identify the operational risks associated with future deepwater operations and specify their plans for responding to those risks, in order to maximize the effectiveness of methods to prevent and respond to potential future releases of hazardous, polluting hydrocarbons. This paper describes a study of public BSEE (previously MMS and BOEMRE) data on incidents involving releases of formation fluids to the environment. The purpose of this study was to provide a factual basis for identifying the operational risk of hydrocarbon releases in offshore operations as a starting point for additional work on identifying opportunities to reduce the frequency, severity, and consequences of such releases, especially for deepwater operations.Incidents reported over the past 15 years were reviewed and organized in a spreadsheet. A total of 90 non-pipeline incidents were identified as including enough description to be useful. Most of these incidents were spills greater than 50 barrels (bbls), but blowouts, fires, and explosions are important and included. To the extent possible, the review determined: the flow path taken from the formation to the point in the well or production system where the fluids were released, the release point, the barriers that were used to reestablish control, and what can these events tell us about potential future deepwater events.It is notable that most of these releases occurred in shelf operations rather than deepwater (water depth ≥ 1,000 ft), which was expected due to the much larger number of wells on the GOM shelf. Nearly two-thirds of the releases happened during active drilling, completion, workover, or well-servicing operations. The remaining events occurred during other operations, particularly production, and include two spills after the wells were plugged and abandoned (P&A’d). The number of blowouts per year was relatively small, varying from 2 to 9 for the 15 year period. The number of blowouts has remained roughly constant despite the recent decrease in the rig activity level. Similarly, the size of most spills was relatively small, if the Macondo event is excluded. Nevertheless, the data gives a factual basis for identifying the kinds of events that could lead to future catastrophes if not prevented or identified and controlled successfully.Copyright