Of all available EOR methods deployed in thin oil rims and gas/oil reservoirs gas intervention techniques seem the most effective 1,2,3,4,5 . The study of practicability of this method was carried out at one of West Siberia gas/oil reservoirs. Natural pressure depletion is the chosen production method for the reservoir in question. Almost 150 wells were drilled within the limits of the reservoir. The dominant production mechanisms are free flow and gas-lift. By the beginning of 2008 average reservoir pressure dropped to 13.0 MPa from the original 28.0 MPa. Decline of formation pressure well below saturation pressure (19.0 MPa) resulted in wells' shutting-in and curtailment of producing well stock. Prevailing causes of well problems are flooding and gas coning while in service. Mean water cut is 10%, GOR is 1600 CUM/MT, while oil production rate of available stock does not exceed 13 MT/D against start-up values of about 100 MT/D.A well drilled next to one of the clusters of the reservoir in question exposed overpressured B4 stratum. Gas flowrates in the well reach up to 106-166 MCUMD with wellhead pressures of 25.0 to 30.0 MPa. This fact encouraged the studies of possibility of gas/oil reservoir pressure maintenance by way of injection of high-pressure natural gas.
Advanced drilling technologies were used on two offshore multiwell platforms in the Lunskoye and Piltun-Astokhskoye fields, in the Sea of Okhotsk to deliver wells that required complex drilling to manage well-to-well collision risk, and to perform underreaming operations, extended-reach drilling (ERD), sidetracking, geosteering, and acquisition of thorough logging-whiledrilling (LWD) data.The project benefited from the successful implementation of a new concept that combined various groups of technical experts within the operating and service companies to address project challenges through proper well planning, 24/7 monitoring, and intervention, when needed, during the execution phase, as well as post-well analysis fed into the planning of subsequent wells.The effectiveness of the collaborative drilling technical team was proven by the overall results since implementing the new concept. Four wells were drilled "shoe to shoe" 25 days ahead of approved for expenditure (AFE) time for the drilling phase. More than 70 proactive interventions to prevent nonproductive time (NPT) were made and delivered to the drilling teams during trial runs; of these, 60% were considered significant and resulted in the implementation of a drilling and engineering operations planning service on subsequent wells. It was the first time in the Lunskoye field that a well had been delivered 8.9 days ahead of AFE for 53.6 days for the drilling phase. The success established good synergy among the client geoscientists and drilling personnel in town, platform teams, including the drilling supervisor (DSV) and offshore drilling engineer (ODE), and service companies providing mud logging services, drilling fluids, directional drilling and LWD services, and bits and underreamers.Thanks to the successful results obtained from the collaborative drilling technical team concept, it has been accepted for use in this major offshore project as it brings continuous improvement to drilling operations through a cyclic process of planning-execution-evaluation.
Авторское право 2013 г., Общество инженеров нефтегазовой промышленности Этот доклад был подготовлен для презентации на Конференции SPE по разработке месторождений в осложненных условиях и Арктике 15-17 октября 2013 года в Москве, Россия.Данный доклад был выбран для проведения презентации Программным комитетом SPE по результатам экспертизы информации, содержащейся в представленном авторами реферате. Экспертиза содержания доклада Обществом инженеров нефтегазовой промышленности не выполнялась, и внесение исправлений и изменений является обязанностью авторов. Материал в том виде, в котором он представлен, не обязательно отражает точку зрения SPE, его должностных лиц или участников. Электронное копирование, распространение или хранение любой части данного доклада без предварительного письменного согласия SPE запрещается. Разрешение на воспроизведение в печатном виде распространяется только на реферат объемом не более 300 слов; при этом копировать иллюстрации не разрешается. Реферат должен содержать явно выраженную ссылку на авторское право SPE. РезюмеПередовые технологии по бурению были использованы на двух многоскважинных морских платформах Лунского и Пильтун-Астохского месторождений Охотского моря для строительства скважин, которые нуждались в комплексных мерах по управлению рисками, чтобы предотвратить столкновение стволов скважин, а также осуществить операции по расширению ствола скважин во время бурения, бурение скважин с большими отходами от вертикали, зарезка боковых стволов, геонавигация и получение полных геофизических данных каротажа во время бурения.Данный проект выиграл за счет успешной реализации новой концепции, которая включала в себя совместную работу различных групп технических специалистов компании «Сахалин Энерджи Инвестмент Компани Лтд» («Сахалин Энерджи») и сервисных компаний для решения сложных задач проекта, путём должного планирования скважин, наблюдения и контроля процессов строительства скважин 24/7, а также оперативного вмешательства в случаях когда это было необходимо в ходе выполнения работ, так же как и анализ полученных результатов с целью использования этих данных для планирования последующих скважин.Эффективность совместной работы технических групп была доказана совокупностью результатов достигнутых со времени внедрения новой концепции. Четыре скважины были пробурены, каждая секция за один рейс, в общей сложности на 25 дней раньше, чем это предполагал согласованный график бурения. Более чем 70 оперативных вмешательств для недопущения непроизводительного времени (НПВ) было установленно и доведено до участников в ходе строительства скважин, 60% из них были отмечены как значительные и представлены к внедрению на этапе инженерного планирования последующих скважин. Впервые на Лунском месторождении скважина была пробурена раньше согласованного графика бурения на 8.9 дня, за 44.7 дня вместо запланированных 53.6 дня. Совместная работа и успех данного проекта установили хорошее взаимодействие между геолого-геофизическим отделом и отделом бурения «Сахалин Энерджи» в городе, командами на платформ...
An operator was drilling complex big-bore gas extended-reach drilling (ERD) wells from an offshore Sakhalin Island platform. Because of the shallow gas anomaly presence beneath the platform, there was a requirement to set an intermediate casing or liner at ~375-m true vertical depth (TVD), which was between the 30-in. driven conductor at 170 to 175-m TVD and the next casing setting depth of 950 to 1065-m TVD. Due to the well complexity and completion requirements, conventional casing design with no underreaming operations was not an option. Well reach and complexity significantly increased since the project started in 2007, which called for improvements in wellbore geometry. The wellbore geometry underwent few changes, concluding with the latest most favorable required for a 27 to 28-in. directional tophole out of a 30-in. conductor with the maximum bit size pass-through diameter of 25-in., and setting 24-in. liner at ~375-m TVD. Originally, these types of topholes were delivered in two separate trips. On the first trip, the 24-in. borehole was drilled with a mud motor bottomhole assembly (BHA), and on the second trip, underreaming-only operations were performed to obtain final borehole diameter. This operation required additional rig time and caused excessive vibrations during underreaming. A different type of underreamer was implemented successfully to eliminate vibrations, but it did not reduce the number of trips. The ultimate solution was to run the underreamer below a bent mud motor, enabling simultaneous drilling and underreaming of the directional top hole while steering the trajectory in a crowded subsurface environment. The presence of deviated conductors with 6 to 8° inclination at the shoe in all outer slots played a substantial role in overall success of the operation. It is very unlikely that the same results could be achieved if the outer slot conductors were straight. Installing the underreamer below the mud motor worked successfully in five recent wells, saving a trip in each well. The tophole trajectory was effectively steered away from the offset wells, creating a no-collision-risk situation. A 24-in. liner was run to the planned depth and cemented. This technique was accepted by the operator for the major offshore project and used as the way forward for the remaining five outer slots. The successful implementation of the simultaneous drilling and underreaming technique demonstrated the benefits and qualitative acceptance of using an underreamer below the mud motor for the directional tophole in this major Sakhalin offshore project. The knowledge and lessons learned from the project can be applied to other worldwide projects with identical or similar casing design requirements.
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