Verma, Chandresh (Saudi Aramco) | ElKawass, Amir A. (Saudi Aramco) | Mehrdad, Nadem (Saudi Aramco) | ElDeeb, Tarek (Saudi Aramco) | Qazi, Muhammad Q. (Saudi Aramco) | Galaby, Amir (Schlumberger) | Salaheldin, Ahmed (Schlumberger) | Fakih, Abdulqawi Al (Schlumberger) | Osman, Ahmed (Schlumberger) | Hammoutene, Cherif (Schlumberger)
While ERD multi-lateral wells in a large Middle East field are typically drilled in six to seven well bore sections, drilling the 8.5-in curve and the 6.125-in lateral sections represents more than 50 % of the total time spent drilling the well. Challenges while drilling the curve section with a motor include difficulty transferring weight to the bit while sliding and differential sticking in the highly poros zones of gas cap. The laterals, which can extend up to 12,500 ft of reservoir contact, are characterized by medium to hard compacted carbonate formations with high stick and slip tendency. This represents several challenges for drill-bit design engineers given that aggressive cutting structures are preferred to generate good rate of penetration even though this often leads to high bottom-hole assembly vibration. Trajectory control, hole cleaning and long circulating hours also represent significant challenges.
This paper will present details of the engineering analysis performed to optimize both 8.5-in and 6.125-in wellbore sections.
For the curve section, the first step was to change the drill string from 5 in to 4 in which considerably reduced the time taken to change the string prior to drilling the laterals. This change of drill string was accompanied by the use of a rotary steerable system and a PDC bit. This was a combination that had never been implemented since the field discovery in 1968. These changes resulted in performance improvements in excess of 50 %.
For the laterals, the engineering analysis resulted in the need of a completely new bit design. The cutting structure was modified to provide a more aggressive bit to formation interaction, and the gauge contact with the formation was enhanced to maintain the bit and BHA stability. The resulting design broke the field rotary steerable ROP record by 28 %. The bit drilled the highest single run footage in the field (12,698 ft) at the highest ROP (96.93 ft/hr) with a rotary steerable system. This was further complemented by optimizing the drilling practices and well bore cleaning practices allowing the elimination of several conditioning trips within the long laterals which resulted in three days of savings in a three lateral well.
The paper will conclude with a discussion regarding the reduced injury exposure that resulted from changing the drill string earlier within the well and a review of further improvement opportunities.
A new riser concept is proposed by Subsea 7 for field development in deep and ultradeep waters: the Tethered Catenary Riser (TCR)-patent pending. The concept consists of a number of steel catenary risers supported by a subsurface buoy which is tethered down to sea-bed by means of a single pipe tendon and anchored by means of a suction pile; flexible jumpers are used to make the connection between the Floating production Unit (FPU) and the buoy. Umbilicals run without interruption from the FPU to their subsea end while being supported by the buoy.
The system has all the advantages of de-coupled riser arrangements: flexible jumpers effectively absorb platform motions, thereby the rigid risers and tendon have very small dynamic excitation. The system can be installed before FPU arrival on site, which improves the time before first oil. Analyses have shown that, with adequate geometry of the buoy, the latter is sufficient stable to induce acceptable tilt and twist when different arrangements of SCRs and flexible jumpers are installed, and under accidental scenarios during the in-place life.
The riser system is best designed for a number of risers between 4 and 8, in addition to a number of umbilicals, thus convenient for one or two drilling centers.
Results of the basic engineering work on the TCR clearly indicate that it is possible to have a robust design using presently qualified materials and technology. The components used in the TCR are all field proven as they are commonly used in existing riser systems.
As a result of installation studies, a method very similar to the one commonly used by Subea7 for Single Hybrid Risers (SHRs) has been selected for the buoy and tether system. Placement of rigid risers, jumpers and umbilicals is as done by Subsea 7 for the BSRs. This method is well adapted for installation by the new Subsea 7 flagship vessel Seven Borealis which is able to perform heavy lift and pipe laying.
The Tether Catenary Riser is a credible option for use in deep water developments all over the world. Since all the components, design methods and installation procedures are fully qualified and familiar to Subsea 7, the concept is cost effective and ready for project application.
Song, Hwa-Cheol (Department of Architecture and Ocean Space, Korea Maritime University) | Doe, Geun-Young (Department of Architecture and Ocean Space, Korea Maritime University) | Han, Min-Bae (Department of Architecture and Ocean Space, Korea Maritime University) | Park, Da-Hye (Department of Architecture and Ocean Space, Korea Maritime University)
An Extendable Draft Semi-submersible (EDS) is a low-motion floating production system concept focused on flexibility and low cost. An Extendable Draft Semi-Submersible (EDS) can support full drilling and production facilities that can be prepared for deployment at a dockside facility with limited water depth. The EDS combines the favorable features of deep-draft Semi-submersibles, Truss Spars and other reduced-heave floaters, making its in-place motions superior to
shallower-draft floaters for supporting dry-tree risers and SCRs.
EDS is a self-installing design, which delivers and deploys a fully operational system without the aid of crane vessels. The EDS structure consists of a floatable deck, stabilizing columns and heave plate/pontoon connected to the bottom of the columns. The barge-type deck is designed to float the entire structure, including topsides, to the near shore site.
Upon arrival, the columns and heave plate/pontoon is lowered down using strand jacks either in a single or dual direction mode and locked into the deck to the locking draft. The use of strand jacks allows the lowering operation to be performed in a higher sea state than normally used for offshore installation thereby increasing the operability. The deck is then raised to the operating elevation by de-ballasting the columns after pawls are engaged between deck and columns for rigid connection between them. The pawl connection between columns and the deck is reversible and the columns can be raised above the deck to enable the platform to be towed to a new location for redeployment or brought to quayside.
An alternative to the self-installing design is installing the topsides by a floatover technique, similar to what has been done for several semi-submersibles in Brazil.
The EDS motions are suitable for Dry Tree application and SCRs in different areas around the world including areas with severe storm environment like Gulf of Mexico, Weastern Australia, etc. The concept provides flexibility in constructing the EDS that facilitates a high level of local content in most areas of the world.
This paper describes the features of the EDS platform along with the fabrication and deployment offshore.
The economic advantage of being able to have a dry tree production platform with a full drilling rig in deep water is well known. These capabilities do, however, indirectly define a number of major system features such as top tensioned risers to provide direct access to the wells, which in turn requires a low motion host vessel.
Extensive life extension studies for a FPSO installation have been carried out. High stressed welds showed too short fatigue lives in as-welded condition. Ultrasonic peening has been selected to extend the fatigue lives of the concerned weld details. The aim with the ultrasonic peening treatment was to avoid any further weld repair and by that contribute to the structural integrity of the installation during its remaining service life.
Fatigue life extension has been achieved by the application of ultrasonic peening to high stressed areas on the pallet stool- and on longitudinal-weld details on the ballast tanks on a FPSO installation.
The fatigue lives for the treated welds were extended to twenty years which is the targeted service life for the installation. Quality Assurance and Quality Control were covered by Ultrasonic Peening Procedure Specification, applied for every treated weld. It ensures that the treatment is exactly reproduced to achieve the expected life extension.
Despite the variable weld quality encountered on the pallet stool welds the treatment was carried out at perfection and it showed to be relatively easy and straight forward application even in locations of difficult access.
The economical benefits due to reduced maintenance as a result of the ultrasonic peening treatment include:
• Avoidance of long term plan for extensive hot work
• Avoidance of long an unscheduled operational disruptions
• Increased structural safety for the installation during remaining service life
• Ultrasonic peening treatment can be applied while the installation is in operation
It is the desire of every operator of an offshore installation to ensure the structural integrity during the targeted service life. In many cases the targeted service life is difficult to achieve alternatively the maintenance costs increase to unacceptable levels.
Therefore an earlier life extension study of the offshore structure suspected to have structural integrity deficiencies increases the chances to keep the installation working safe for the original alt. extended design life as well as to keep the maintenance costs under acceptable level. An extensive life extension project is being carried out on FPSO Triton . One of the remedies used to achieve the targeted service life on this installation is the ultrasonic peening treatment of weld connections subjected to high stresses.
Technology Focus - No abstract available.
This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 134563, "Continuing Application of Torque-Position Assembly Technology for API Connections," by J.P. Powers, SPE, ExxonMobil De velopment Company, and M.S. Chelf, SPE, ExxonMobil Upstream Research Company, originally prepared for the 2010 SPE Annual Technical Conference and Exhibition, Florence, Italy, 19-22 September. The paper has not been peer reviewed.
Logging while drilling (LWD) tools acquire data with a time index and record data over most of the time the bottom hole assembly (BHA) is in the borehole (all when batteries are present). Depth-indexed data is extracted from the larger time-indexed acquisition data set. The time-indexed data is rarely requested or presented for evaluation. However, these time-indexed measurements contain great potential for understanding the reservoir. The opportunity exists to use stationary LWD data as a direct dynamic measurement of the formation and movement of fluids. These dynamic measurements can provide information on the quality of the mudcake at the time of measurement. There are also conditions where flowrates and, by inference, formation permeability can be derived from these time-based measurements (i.e., effectively injection logs while drilling).
The examples shown illustrate some of the untapped potential that exists with every LWD data acquisition run, beyond the normal processing with depth-indexed data. Significant opportunities exist with this time-based data, from enhanced-quality measurements to the interpretation of dynamic downhole data.
3-D streamlines provide an effective tool for reservoir management because of their ability to display reservoir flow and well connections in a physically intuitive manner. Streamlines have been extensively used to investigate the interaction between heterogeneity and well patterns and also for rate allocation and pattern balancing. More recently, streamlines have been used in conjunction with constrained optimization techniques for improving waterflood performance via rate control. Field scale rate optimization problems, however, involve highly complex reservoir models, production and facilities constraints and a large number of unknowns, making them inaccessible for routine waterflood management.
In this paper we provide a simple and easy to use workflow for waterflood rate optimization using streamline-based flood efficiency maps that display the flux and time of flight distribution amongst producing wells. We demonstrate the use of flood efficiency map to optimize the injection/production rates to maximize waterflood sweep efficiency by equalizing the average time of flight (TOF) amongst the producing wells in regional basis. Our optimization approach is extremely efficient because it relies on simple analytic calculations to compute weighting factors for injection and production rates to minimize the TOF variance amongst producing wells. Because the approach does not rely on formal and complex optimization tools, it is particularly well-suited for large-scale field application. Also, the approach can be used with both streamline and finite difference simulators. For finite-difference simulations, the streamlines and time of flight are derived from the flux field generated by the simulator. Multiple examples are presented to support the robustness and efficiency of the proposed waterflood management scheme. These include 2D synthetic examples for validation and a 3D field application.