Design and Construction of ERD Wells at the Semakovskoye Field
Introduction
RusGazAlliance (a joint venture between Gazprom and RusGazDobycha) together with RusGazBurenie successfully completed the construction of the longest onshore extended reach well (ERD) in Russia on Senomanian deposits.
Well No. A08 at the Semakovskoye field was 3,663m long with a vertical depth of 879m and a vertical deviation of 3045m.
RusGazBurenie, the general contractor for well construction, drilled the record well using the latest technologies from leading Russian and international oil and gas service companies. The Customer’s specialists, the General Contractor and subcontractors successfully collaborated to implement new well construction technologies, whilst having an excellent field health and safety record. It should also be noted that special attention was paid to environmental preservation, which is important, given the geographical location of the project being carried out in the coastal area of the Taz Bay in close proximity to the Kara Sea Shelf. There are an abundance of bays, rivers and lakes. Production operations increase the environmental and industrial safety requirements for the field that has difficult ice and permafrost conditions, and requires the protection indigenous populations and their farmlands as well as the habitats of rare and endangered species of plants and animals.
The common task of operators and service companies is to increase the efficiency of any subsoil development. This can be solved through a flexible and highly qualified approach to the development of deposits. It is obvious that the development of the oil and gas sector directly depends on the quality of its servicing: drilling, well workover, maintenance of equipment downhole and on the surface. The most prompt response to the challenge of time is modernization and innovation.
About the Project
The Semakovskoye field is located in the territory of the Tazov and Nadym districts of the Yamalo-Nenets Autonomous Okrug and in the coastal area of the Taz Bay and Kara Sea. The field was discovered in 1971. The gas content of the Semakovskoye field is produced from the Cenomanian deposits.
The license for exploration and production of hydrocarbons within the Semakovsky area belongs to RusGazAlliance.
• In 2008, three wells were drilled in the offshore section of the field.
• In 2009, three more wells were drilled in the coastal area of the Taz Bay.
• The regional center is the village of Tazovskiy, located 220km to the south of the Semakovskoye field.
The region is not economically developed, the nearest settlement is the Anti-Payuta settlement, located 50km from the opposite bank of the Taz Bay. Novy Urengoy City and Yamburg settlements are located 320 km to the south and 80 km to the south-west, respectively.
The delivery of equipment, materials and goods is carried out by railroad, Novy Urengoy City – Yamburg station, as well as along the road from Novy Urengoy to the port of Yamburg City. The conditions for the transportation of goods and drilling equipment to the area of the field are difficult. There are no roads in the region, so the main volume of cargo transportation is carried out during winter along specially laid temporary roads (winter roads). The winter roads are open from December to May. The roads are supplemented with crossings over water ways (rivers and channels) and swampy areas. In summer, cargo can be delivered to the site via water. The navigation period is from July to September. In addition, aviation is used for cargo and transporting in personnel.
The nearest fields are the Severo-Parusovoye oil and gas condensate field located in the southwest at a distance of 10km, and the Tota-Yakhinskoye gas field located at a distance of 30km to the north.
The nearest field to be developed is the Yamburgskoye oil and gas condensate field located to the south at a distance of 60km. Gas transportation from the Yamburgskoye oil and gas condensate field is carried out through the Yamburg-Center gas trunkline system, and a condensate pipeline Yamburg – Urengoy has been built for condensate transportation.
Drilling the Semakovskoye field is a unique project which is implemented in remote area with no infrastructure.
Within the framework of the project 19 production wells will be delivered in 2022 with high vertical displacement and a section up to 4400 meters long under the shore of the Tazovskaya Bay. Wells are being constructed on the PK-1 reservoir (Cenomanian reservoir).
Ahead of the schedule, the construction of wells in the second cluster were successfully completed, 13 production wells were drilled with a total penetration of 34,758 meters, at an average commercial speed of 2,384m / rig-month. The maximum commercial speed reached was 3525m / rig-month at well № A04.
The project used the most advanced equipment of Gazprom Burenie, the drilling contractor, including the ZJ-50 DBS Drilling rigs, as well as the ZJ-70 Drilling Rig, train type. The Drilling rigs are equipped with a top drive, three mud pumps, four-stage mud cleaning systems, automated tongs, and computerized drilling control systems.
To increase drilling efficiency and maintain reservoir properties maintenance at the Semakovskoe field, a unified system was established to verify the engineering and technical solutions of the service contractors, con-cerning the compliance with requirements for operating drilling efficiency, safe well construction, maintaining the initial reservoir porosity and permeability and a rationale for well completion system:
1. A method was developed for safely replacing the oil-based muds with completion fluids, based on the results of laboratory testing with the use of the core material from the Semakovskoe field.
2. Recommendations were developed during the pre-design period, together with the participation of the engineering contractors, for improving the cleanout treatment systems at the Semakovskoe field’s БУ ZJ-50 drilling unit; an efficient system was developed for location, storing and use of fluids in the tank farm by way of visualizing the use of tanks (vessels) at each intermediate stage of the well con-struction process.
3. A laboratory study on drilling mud was developed to assess and manage the technological risks of the project’s mud program which consists of the following:
a. Determine the basic parameters of the process fluids;
b. Determine the kinetics of a blank plug break-up in the inflow control devices and the direct-thread well screens;
c. Determine the chilling temperature for salt brines
and drill mud filtration cake destructive compositions;
d.Run a X-Clean testing using the shelf liquid oil-based
mud solution according to contractor’s standard;
e. Compatibility of flush fluids with the destruction compositions and oil-based solutions;
f. Determine the permeability of the filter element in various media;
g. Assess the corrosivity of fluids towards the well completion components;
h. Testing the compatibility of the completion brine and solution products with the ПК-1 rocks, regarding the secondary emulsification;
4. To assess and manage the project’s technological risks with regard to the well cementing program, a laboratory testing study of cement mud was organized which includes the tests for cement used while setting casing strings of various diameter (conductor casing, surface casing, production casing). One of the key features of this research has been the use of API standards for well casing carried out un-der the arctic conditions; a system of check lists has been developed to assess the status of the well cementing stock prior to each operation, as well as a program was developed for a rapid laboratory quality control of the cements prepared under various ambient temperatures of the environment.
5. Well Construction provided with premium lower and upper completion systems, which includes the next types of well design:
Lower completion:
Well Design #1:
a. Premium Direct Wrap Screens with dissolvable plugs on a perforated base pipe
Well Design #2:
a. Premium Direct Wrap Screens with dissolvable plugs on a ICD (inflow control devices) premium ports
b. Open-hole swellable packers for zonal isolation
Upper completion
Downhole Monitoring Systems (DTS (distributed temperature sensors) with pressure gauges)
6. To assess and manage the project’s technological risks, with regard to production rates and the evalu-ation of the completion system efficiency, a program was developed providing a detailed list and se-quence of engineering calculations giving the rationale for the estimated well flow rate, which in-cludes the Nodal Analysis, making it possible to provide safe, hydrate-free well operations, compati-bility of the Christmas tree and downhole monitoring system, and the calculations of computerized fluid dynamics (CFD) for the wells of the #2 design, taking into account the pressure drops taking place in the micro-annulus.
To improve drilling efficiency and preserve the fluid-bearing properties at the Semakovskoye field, an oil-based drilling mud (OBM) is used in combination with the high-tech drilling equipment – an RSS (Rotary Steerable System) and WLT (Well Logging Tools), which help optimize drilling parameters and obtain high-quality real-time geophysical data for effective geonavigation support to increase the targeting of the wells in the most productive reservoir sections.
The Semakovskoye field is located in a aquatic protection zone which requires the highest level of drilling process compliance with the nature protection legislation of the Russian Federation. Therefore, the field is developed with pitiless drilling and the removal of drilling cuttings. The drill cuttings were drained using a mobile unit for draining sludge to reduce the humidity of drilled cuttings.
It is fundamentally important for the company to ensure a high level of industrial and environmental safety in order to preserve the unique nature of the region.
The company implemented and certified quality management systems, safety and health, environmental management for compliance with the requirements of international standards ISO 9001: 2015, BS OHSAS 18001: 2007 and ISO 14001: 2015.
About ERD Wells
The geological structure of the field also determined the development system – since the main reserves of the field are in the shelf of the Tazovskaya Bay, well pads are located along the coastline, and wells reach out to the sea. After the relatively simple wells were drilled, it was time to construction the ERD wells. The economic and technical analysis has shown that the construction of extended reach wells is the most economically and environmentally effective solution to gain access to the remote reservoirs of the Semakovskoye field.
Economic efficiency means the optimization of investments in the development of the infrastructure required for the development of the field in order to increase profits.
ERD wells (in the world classification – Extended Reach Drilling) – wells with an extended reach from the vertical, with a deviation ratio to vertical of more than 2: 1. The characteristics of this type of wells are:
• high mechanical loads – increased axial loads and often excessive torque due to high values of the friction coefficient due to the large length of the highly inclined section of the wellbore;
• high hydraulic loads – annular pressure is several times higher compared to even horizontal wells with lower bottomhole displacement from the vertical, not to mention vertical wells (even deep ones);
• difficult cuttings removal from the wellbore , especially when designing wells with a high PHAR value (pipe- hole area ratio) – the higher the PHAR, the more difficult it is to remove waste;
• difficulties with reaching casing strings and liners – high coefficients of friction and insufficient weight of the upper part to reduce the force of «pushing» the strings;
• problems of borehole well stability and narrow mud weight window;
• problems with delivering the load during drilling, as well as during the final operations, for example, creating the necessary load when hanging liners;
• in addition, due to the large remoteness of targets, additional geological uncertainties arise in structures that are heterogeneous in strata and strike.
An ERD well is not just a more complex directional well. The basis for success in the construction of such wells is: the use of advanced technologies, the professionalism of employees, the correct organization of processes and well-established communication between the various participants in the project. That is why preparations for the record-breaking wells began long before drilling began. Well design was carried out with the involvement of the drilling contractor, and the technical specialists of the service companies specializing in drilling ERD wells. At the design stage, various criteria and factors were taken into account and analyzed – design structure and well trajectory (including the first section curvature parameters and trajectory reversal), correct selection of drilling tools, drilling surface equipment, stability of the wellbore, solving problems with cleaning the wellbore – transporting cuttings to the surface, monitoring the drilling parameters and equivalent circulating mud density in real time, as well as technologies for running and cementing casing strings and attaching screens. Prior to drilling the wells the changes considered in the geological data and promptly made adjustments to the project. At the same time, special attention was paid to the assessment of operational risks and the preparation of an emergency action plan.
About the Record Well
Geomechanical drilling support was used during the construction of wells together with the building and updating the model for each well. Key technologies with directional drilling, fluids and bits, and well casing were applied in close cooperation with geomechanical engineers and geosteering engineers, as well as with the drilling contractor.
On the 10th March 2021, the construction of a unique high-tech well № A08 was completed. The well has a target depth of 3,663m with a vertical depth of 879 m and a vertical deviation of 3045m. Today, this is the longest ERD (Extended reach drilling) well of a similar design on the Cenomanian deposits in the Russian Federation (the vertical – ERD ratio 3.46).
The previous record was recorded in 2015 at the Yurkharovskoye field, where Gazprom Burenie completed the construction of a turnkey well for the Senomanian deposits with an ERD coefficient of 2.28 (bore length 3168m, offset 2483m with vertical 1090m ).
The achievement of this result opens up new perspective for the development of hydrocarbon reserves at the Semakovskoye gas field under the coastal area of the Tazovskaya Bay.
Geomechanical Support
Before embarking on the development of the project, special attention was paid to risk analysis, assessment and prevention.
As noted earlier, ERD wellbore stability posed a major challenge when drilling, especially when drilling high zenith angles through shale intervals. At the Semakovskoye field, there are additional specific problems associated with wellbore stability:
• Depletion of the productive formations and a reduction in formation pressure, which contribute to the reduction of fracturing pressure and lost circulation;
• Presence of unstable clay intervals, especially the “chocolate clay” interval.
The presence of both features at the same time significantly narrowed the safety corridor for the drilling fluid and made had a significant impact on the (in terms of wall stability) density of the drilling fluid.
One of the key decisions was the use of geomechanics before drilling and in real time. The geomechanical model, in the planning stage, made it possible to determine the “difficult” intervals and safe boundaries for the equivalent circulation density, on the basis of which the choice of solutions and technologies were made. To obtain the most accurate values of the safe boundaries of the equivalent circulating density, the geomechanical model was updated based on the results of the BHA logging tools. Based on the equivalent circulating density recorded from the bottomhole pressure sensor, the drilling modes were selected that ensure that all operations remained within the defined safe limits. To ensure trouble-free wiringof the interval, a specially selected formulation of the drilling fluid was selected that provided acceptable equivalent circulating density values and low friction coefficients. Based on the results, the drilling and cleanout modes, the speed of tripping and running operations and forward / back reaming, as well as the controlling the speed of the casing strings and liners as they are RIH.
To ensure trouble-free drilling at the pre-drilling modeling stage, the models of the mechanical properties and the calculations of wellbore stability were performed.
The main purpose of calculating the wellbore stable state for the planned well trajectory is to determine the boundaries of the equivalent density of the drilling mud, understanding this avoids any problems with wellbore stability. In the course of this study, the fracture gradient, the collapse gradient, the calculation and calibration of the elastic properties of rocks in the near-wellbore space and the wellbore stability calculation are conducted to determine the safe window for the specific weight of the drilling fluid, to determine the risks associated with the instability of the wellbore.
A Unique Set of Technologies for Well Construction
Even at the planning stage, an important and correct decision was taken before the implementation of the project, an engineering consulting company that specializes in the design and support of ERD wells was engaged to examine the design solutions. An extended range of engineering calculations were performed on the profiles of two wells in the first drilling phase. Based on the results of the extended engineering calculations and the assessment of the design solutions, a detailed report was prepared with the results of engineering calculations, conclusions and recommendations and risks, which were subsequently included in the «program for well construction», and this also made it possible to change some of the materials and equipment.
Particular attention was paid to the selection of the correct drilling technologies. The selections were based on careful and detailed planning, modeling of borehole and ground conditions and evaluating the results of a combination of different technologies. Selecting the correct drilling system to obtain the best results cannot be underestimated, as many operating conditions, such as wellbore stability, do not allow for trial and error, should the worse happen, it could affect the construction of that section and, in some cases, the well as a whole.
Bottom-Hole Assembly
Currently, the proposed rotary steerable system is the optimal solution for drilling ERD wells, since they provide directional drilling with continuous rotation of the drill string, i.e. create conditions for efficient cuttings removal, which minimizes the risks of the BHA becoming stuck.
The rotary steerable system allows for 3D control of the borehole’s deflection as the drill string rotates.
To achieve the optimal drilling performance, the drilling modes and well placement data acquisition was collected in real time, MWD/LWD tools were used, multifunctional logging tools for neutron porosity, density, resistivity imaged mapping-while-drilling were used in combination with the rotary steerable systems and PDC bits.
The results of the ERD technologies and practices implemented during the construction of the production wells at the Semakovskoye field have opened up new prospects for onshore wells targeting the development of hydrocarbon deposits under the coastal areas of the Taz Bay. They can also be successfully applied to the development of northern and arctic fields.
We are not limited to these results, already the specialists of RusGazBurenie and RusGazAlliance have started appraisal work on the second phase of the Semakovskoye field’s well development program, where it is planned to drill even more complex ERD wells, with lengths of 7000m (the ERD coefficient will be greater than – 7.3). The project has shown that it is very effective, at every stage of development, to use a systematic approach to project management and implementation. At the moment, a working group has been created to conduct technical assessments and selection and to monitor the market for the most advanced ERD technologies. Determining the right technologies and optimal engineering solutions, at the design stage, is a key component for the successful implementation of such projects.
Authors
RusGazBurenie LLC: I. Mukhametshin, S. Doronin, D. Baryshev, T. Magomedov, S. Antipov
RusGazAlliance LLC: I. Sharifullin, R. Borschev, T. Zhiltsova, R. Valeev
