Underbalanced Coiled Tubing Drilling Research Articles

TECHNOLOGICAL SOLUTIONS FOR DRILLING USING FLEXIBLE TUBING – UP-TO-DATE WORLD EXPERIENCE AND PROSPECTS FOR RUSSIA

The article presents an analytical review of modern technologies for using flexible tubing to perform complex technological operations aimed at increasing oil recovery, exploration and repair of wells, and construction of lateral and horizontal wellbores. The authors have been most interested in the technology of underbalanced coiled tubing drilling, since it has the potential to increase oil production while maintaining or minimizing drilling costs without drilling complications while ensuring operational safety.The experience of a foreign company in coiled tubing drilling is reviewed, positive results and growth points are highlighted. Solutions for the implementation of coiled tubing drilling in Russian conditions are proposed to reduce the costs of constructing horizontal wells and additional hydrocarbon production during the drilling process. Preparatory work is underway to conduct pilot-industrial research of the proposed technology.

Underbalanced Coiled Tubing Drilling: Delivering Well Production Safely in High H2S and Tight Gas Reservoirs, UAE

Summary United Arab Emirates (UAE) is seeking to become self-sufficient in gas supply by 2030. This has led the country to initiate several exploratory and appraisal projects to achieve this goal. This study covers one such pilot project targeting production from tight gas reservoirs in three wells through a coiled-tubing (CT) underbalanced drilling (UBD) project in ADNOC Onshore. CT pressure control equipment (PCE) was rigged up on top of production trees with wells already completed and cemented. A CT tower was used to accommodate the drilling bottomhole assembly (BHA) and eliminate risks related to its deployment. CT strings were designed to reach target intervals with sufficient weight on bit (WOB), suitable for sour environments, and able to withstand high pumping rates with mild circulating pressures. To address the hazards of H2S handling at the surface, a custom-fit closed-loop system was deployed. The recovered water was treated on the surface and reused for drilling to decrease the water consumption throughout the operations. The plan was to drill 3 3/4-in. horizontal laterals in all candidate wells. Each well was completed with a combination of a 4 1/2-in. and a 5 1/2-in. tubing and a 7-in. liner. Five laterals were drilled across the three candidate wells targeting carbonate reservoirs with each lateral having an average length of ~4,000 ft. The achieved rates of penetration varied significantly from 15 ft/min to 30 ft/min while drilling through the various formations. Over the course of the pilot project, several challenges had to be addressed, such as material accretion on the CT string during wiper trips, treatment of return fluids having high H2S content and rock cuttings, and ensuring the integrity of the CT pipe while operating in severe downhole environments. Solutions and lessons learned from each well were implemented subsequently in the campaign, such as the use of increased concentrations of H2S inhibitor to coat the CT string, the use of nitrified fluids based on changing well parameters to maintain underbalance, thorough pipe management through real-time CT inspection, and adding a fixed quantity of fresh water to the drilling system every day to avoid chemical reactions between the drilling fluid additives and hydrocarbons. The wells completed with this method exceeded production expectations by 35–50% across the project while reconfirming the value of the technology. The use of CT for UBD is still considered a challenging intervention worldwide. Such cases in high H2S environments are rare. This study outlines best practices for a CT UBD and a setup that can be replicated in other locations to implement this methodology with high H2S and when rig sourcing is a concern.

Engineering Approach Uses Underbalanced Coiled-Tubing Drilling

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210978, “Novel Engineering Approach Using Underbalanced Coiled-Tubing Drilling Solutions for Tight Sour Gas Carbonate,” by Mohamed Osama Abd El Meguid, Ayman El Shahat, and Ali Sulaiman Bin Sumaida, ADNOC, et al. The paper has not been peer reviewed. _ Because of declining reservoir pressures in some of its onshore gas carbonate fields, the operator initiated a three-well underbalanced coiled-tubing drilling (UBCTD) campaign in its onshore Asab and Bab fields, with two wells to be drilled in Asab and one in Bab. Because of the high hydrogen sulfide (H2S) content, a closed-loop system—the first one successfully implemented in the Middle East, according to the authors—was implemented. The complete paper discusses the design and planning involved in the drilling of these three wells, the operational challenges encountered, and mitigations used. Introduction One of the operator’s main objectives was to increase production while safely maintaining or minimizing operating costs. One method of achieving these goals is the use of coiled tubing (CT) to drill formations in underbalanced mode. The Asab and Bab fields are southwest of Abu Dhabi. Both fields have high H2S and CO2 content, with a bottomhole temperature of approximately 260–270°F. The candidate wells were drilled conventionally until the top of the reservoir section; then, the UBCTD package was moved to drill the reservoir section in underbalanced mode. The typical well completions, from top to bottom, include the following: - 5.5-in. tubing - 4.5-in. tubing - 7-in. liner - 100 ft of 6-in. openhole Project Objectives Because of safety and logistical constraints, the project would use a closed-loop system and recirculate the drilling fluid, thus avoiding high water consumption. Also, the system needed to be designed to safely handle H2S in return fluids. UBCTD using a closed-loop system has been performed elsewhere but not in a high-H2S and high-CO2 environment. Trajectory Design and Tubing Forces Trajectory design is an important part of drilling operations; reservoir targets given by geologists and reservoir engineers must be met. To expose more drilling footage in producing formations and to increase overall productivity, the geologists provide formation-top coordinates so that the drilling engineer knows how to proceed as drilling progresses through the reservoir subunits. When the well trajectory was designed in the discussed case, the CT engineer input planned well surveys into software so that the CT forces could be analyzed. Because these predrilled wells had never had CT interventions, the friction coefficient was unknown and the outcome of the software could have been very different from that observed while drilling. Friction coefficients from other conventional CT operations within the UAE, as well as those from other CT drilling operations in the region, were reviewed and then used for analysis. With the lowest friction coefficient of 0.3 for open hole, the target drilling length could not be achieved. Project planning required a solution to enable the lateral to meet the proposed objectives.

Overview: Coiled Tubing Applications (June 2007)

After reviewing paper abstracts from many SPE venues for this last year, it became clear that coiled-tubing (CT) drilling is still generating much interest in the oil field. Yet with all the interest, few (perhaps with the exception the Canadians) are actually applying the technology in their wells. CT drilling is still striving for recognition, acceptance, and maybe just a little respect, as it has for longer than most would realize. While researching material for a presentation several years ago, I found it surprising to discover just how old the concept of CT drilling really is. Most would guess CT-drilling technology dates back to the early to mid-1990s, and some of the CT-savvy Canadians often will move that date back to the early 1970s. However, the US patent office contains information disclosing the idea of using reeled conduits for "well boring" with a filing date of May 1926. While this early concept discussed the use of hose as a conduit, the idea of using rigid pipe for "well drilling" has a filed date of February 1948. Interestingly, these ideas were not just paper patents—the technology was applied in various forms starting in the mid-1930s. Over the ensuing years, CT-drilling technology was used both onshore and offshore. Discussions of the success in this early work include a phrase that still is used to describe some CT-drilling activities today: "It was a technical success." While many will argue the merits of the use of CT-drilling equipment in an arena that often is considered the exclusive domain of rotary-drilling technology, fewer will question the value of CT to fill other completion voids previously performed by a drilling unit. One such example is CT fracturing, which gained rapid acceptance in many areas throughout the world as a viable tool to quickly, efficiently, and economically isolate and fracture numerous pay zones in well. And with the advent of high-angle and horizontal wells, many areas throughout the world use CT to perform tasks normally associated with slickline, wireline, or jointed-pipe techniques. Dozens of companies are providing new tools that enable CT to perform these needed functions economically, as documented in SPE papers. Considering history, CT-drilling units will not displace rotary-drilling units. Neither will CT units make slickline, wireline, or snubbing units obsolete. However, if properly engineered and applied, CT's versatility allows it to perform a wide variety of services throughout the drilling, completion, and intervention arenas. This year's SPE papers validate this claim. Coiled Tubing Applications additional reading available at the SPE eLibrary: www.spe.org SPE 101065 "Near a Kilometer of Perforating Guns, in a 71/2-km, Extended-Reach Well—Coiled Tubing Shows Its Mettle in New Zealand" by P. Bartholomew, Shell Todd Oil Services, et al. SPE 106907 "Successful Application of Underbalanced Coiled-Tubing Drilling in Horizontal Short-Radius Re-entry Well in Hassi Messaoud, Algeria" by Bachir Ben Amor, Sonatrach, et al. SPE 102608 "3D Managed-Pressure Drilling Around a Salt Dome Using Coiled Tubing: A Case Study—Challenges and Solutions" by Abdul Mujeer Abdul Rehman, SPE, Maharashtra Institute of Technology SPE 102661 "Fill Cleanout With Coiled Tubing in the Reverse Circulation Mode" by J. Li, BJ Services, et al. SPE 107113 "Fatigue Life of Coiled Tubing With External Mechanical Damage" by T. Padron, BJ Services, et al.

Overview: Coiled-Tubing Applications (June 2005)

Having been involved in coiled-tubing (CT) technology for many more years than I care to admit, it is interesting to see how much has changed during the last quarter century. Improvements in CT manufacturing, materials, equipment design, and computerized monitoring, as well as a better understanding of CT mechanics, set the stage for rapid growth and acceptance of CT as a viable and versatile oilfield tool. I firmly believe that, following this initial technology surge, the advent of various knowledge-/experience-sharing conferences and joint-industry projects, focused solely on CT technology and needs, have accelerated this CT “revolution.” The first technology-transfer gatherings I recall attending were the HydraRig-sponsored forums beginning in 1989 through the World Oil CT conferences beginning in 1993. There also were several other public and intercompany events offering forums for CT pundits during the 1990s. In 1996, recognizing the need to share ideas on a larger scale, the Intl. Coiled Tubing Assn. (ICoTA) introduced its roundtable conferences. ICoTA soon teamed with SPE to bring us what is now considered the premier CT technology-transfer forum. This year, estimated attendance at the 2005 SPE/ICoTA Coiled Tubing Conference and Exhibition was 880—up 100 from last year—not including an additional 57 Texas A&M U. students we “graying” technologists were happy to welcome. As I was reviewing papers from recent SPE and SPE/ICoTA conferences for this month’s feature on CT technology, it became apparent to me just how much the focus of the CT conference papers has changed. It seems to me that most early-conference papers centered around CT mechanics—on why CT behaves the way it does and predicting when it will break—and around successful CT jobs for any number of applications. Recent offerings focus more on mainstream issues and what I call CT exploitation. - Reducing the cost and extending the market for CT drilling services. - Improving operational and safety efficiency. - Discussing successful CT programs. - Delivering solutions to complex problems in areas lacking economically viable alternatives. And, of course, there still are the ubiquitous novel and unique thought-provoking sub-jects the innovative CT community is known for. Additional Coiled-Tubing Applications Technical Papers Available at the SPE eLibrary: www.spe.org SPE 92513 Underbalanced Coiled-Tubing Drilling: Update on a Successful Campaign SPE 94058 Some New Developments Applicable to Coiled Tubulars SPE 94159 World’s First Utilization of Coiled Tubing to Dissolve Hydrate(s) in an FPSO Riser: Case History SPE 94102 An Effective Sweep-Cleaning of Large Deviated Wellbores Using Small Coiled-Tubing Systems SPE 90558 Effect of Coiled-Tubing Curvature on Friction-Pressure Loss of Newtonian and Non-Newtonian Fluids—Experimental and Simulation Study

Wired BHA for Underbalanced Coiled-Tubing Drilling

This article is a synopsis of paper IADC/SPE 59161, "Wired BHA Applications in Underbalanced Coiled- Tubing Drilling," by Scott K. Tinkham, SPE, Dale E. Meek, SPE, Timo W. Staal, SPE, Schlumberger Oilfield Services, originally presented at the 2000 IADC/SPE Drilling Conference, New Orleans, 23-25 February.

Industry Guidelines for Underbalanced Coiled-Tubing Drilling of Sour Wells

This article is a synopsis of paper SPE 54483, "Industry Guidelines for Underbalanced Coiled-Tubing Drilling of Critical Sour Wells, " by H.B. Luft and G. Wilde, SPE, BJ Services, originally presented at the 1999 SPE/ICoTA Coiled Tubing Roundtable, Houston, 25-26 May.

Designing Under- and Near-Balanced Coiled-Tubing Drilling by Use of Computer Simulations

Summary This paper describes the use of two computer simulation utilities to design underbalanced or near-balanced coiled tubing drilling: one is a steady-state design module and the other is a transient wellbore simulator developed for coiled-tubing operations. The steady-state design module provides various design parameters for a drilling operation, and the transient wellbore simulator predicts the outcome from a particular design for the entire operation. Simulation results show the desired under or near balance can only be achieved by certain combinations of liquid and gas rates when using foam as the drilling fluid or using gas injection through gas-lift mandrel or parasite string. The effects of cuttings loading, depth of injection point and reservoir inflow on the downhole pressure or underbalance are presented and discussed. A procedure for designing under- or near-balanced drilling is described and demonstrated with an example using the computer utilities. A field example is used to show the accuracy of the simulator by comparing the measured and simulated downhole pressures.