Well-Control Analyses on Extended-Reach and Multilateral Trajectories
- Jonggeun Choe (Seoul Natl. U.) | Jerome Schubert (Texas A&M U.) | Hans Juvkam-Wold (Texas A&M U.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- June 2005
- Document Type
- Journal Paper
- 101 - 108
- 2005. Society of Petroleum Engineers
- 1.10 Drilling Equipment, 1.6.1 Drilling Operation Management, 1.7.5 Well Control, 1.6.6 Directional Drilling, 4.3.4 Scale, 4.1.9 Tanks and storage systems, 2 Well Completion, 1.2.1 Wellbore integrity, 5.1.1 Exploration, Development, Structural Geology, 6.1.5 Human Resources, Competence and Training, 1.6 Drilling Operations, 1.7.6 Wellbore Pressure Management, 3 Production and Well Operations, 5.7.2 Recovery Factors, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.3.2 Multiphase Flow
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For economic and technical reasons, the industry has used directional,extended-reach, horizontal, and multilateral wells. Although technologies arewell developed for these wells, and there are numerous successes in the lastdecade, these wells still have high level of risk in drilling and completion.Well control is one of the relatively unanswered, but important, operationsbecause improper well control followed by a blowout is one of the mostexpensive and feared operational hazards.
To maintain a specified bottomhole pressure (BHP), surface choke pressureshighly depend on kick vertical height in the well and well trajectory. As thefinal hold angle of the well increases from vertical, shut-in casing pressure(SICP) reduces to shut-in drillpipe pressure (SIDPP) and remains the same aslong as the kick stays in the horizontal section. For equal vertical depths,the maximum choke pressure is insensitive to hold angles or hold lengths, aslong as the initial pit-volume gain is the same. However, for directional andextended-reach wells, choke pressure can increase, even without kick expansion,because of the gain of kick vertical height in the build section. This may maskchoke-pressure reduction because of larger annular capacity when the kickpasses the casing shoe, especially if the kickoff point (KOP) and casing-shoedepth are close.
In multilateral wells with more than one kicking wellbore, SIDPP is affectedby both formation overpressure and kick size in each wellbore. The maximumvalue among them will appear at the surface. Therefore, we should be careful inthe interpretation of the shut-in pressures. For safe kick circulation, we mustconsider additional pressure to compensate for hydrostatic-pressure reductionresulting from kick migration and expansion in branch wellbores.
For economic and technical reasons, the industry has used directional,extended-reach, and horizontal wells. Directional drilling is used to direct awellbore along a preplanned path to a target located at a given distance fromthe vertical. We can calculate its trajectory accurately if directional datasuch as measured depth, inclination angle, and azimuth are known.1 For theplanning of the well trajectory in a two-dimensional plane, we can usegeneralized equations,2,3 which are applicable for directional and horizontalwells, rather than using composite buildup charts or several directionalequations, depending on each trajectory type.
Several wells drilled from one platform for offshore development will reducethe development cost significantly and make the installation of productionequipment efficient. These wells are also applicable for areas that will notpermit vertical wells because of inaccessible obstructions, limited spaces, orenvironmental concerns. Multiple targets can be reached by a single directionaltrajectory.
From the production point of view, horizontal or near-horizontal wells areused to enhance recovery efficiency by increasing reservoir exposure or byintersecting fractured reservoirs. It can also reduce chances of water coning,especially for a thin reservoir. They have been used extensively in heavy-oilreservoirs. In the early 1990s, the industry employed multilateral wells fromwhich multiple wellbores are drilled from one main wellbore (also called the"parent" wellbore). Multilateral wells have the same aforementioned advantages.However, implementation will be much more complex than that of directionalwells with a single wellbore.
Although technologies are well developed for these wells, and there arenumerous successes in the last decade,4,5 these wells still have a high levelof risk concerning drilling, completion, pressure imbalance, communicationamong laterals, and production management. It will require multidisplinaryteamwork, thorough planning, and implementation as planned. Because wellcontrol is one of the relatively unanswered but important operations, we mustdevelop a firm well-control plan for practical applications of these wells.
A kick is defined as an unscheduled flow of formation fluids into awellbore. Well control includes several activities for kick prevention, kickdetection, kick confinement, and kick removal with safe and efficientprocedures. The best way of controlling kicks is kick prevention, which may beachieved through sound and thorough planning and execution.
|File Size||468 KB||Number of Pages||8|
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