Weatherford has been mobilizing a bucking unit equipped with torque/turn process control systems to an operator’s onshore Australian support base and providing full pipe preparation. Weatherford’s Aaron Sinnott explains how these services significantly reduced operating costs.
Until recently, most aspects of tubular handling and running preparation have been carried out on the rig floor offshore, a process that requires significant manual handling. Typically, tubulars were shipped to the rig and laid out on pipe racks while processes such as cleaning, tallying, thread inspection and drifting were carried out off line by the rig crew, before the pipe could be run in the hole. The number of personnel required to manually carry out these operations on a rig deck of limited space introduced significant risks to safety and efficiency.
While newer offshore drilling rigs are equipped with auxiliary pipe make-up stations and racking systems for offline pipe handling and preparation – which can provide major cost savings – they have lingering limitations. For example, the capacity for 135/8in diameter and larger casing that can be racked in the derrick is usually lower than the amount required for hole sections in deeper wells.
As a result, service companies that normally provide tubular running services are now assuming responsibility for all aspects of tubular management, such that there is a cohesive focus on drilling operations. In Australia for example, service providers are being called upon to deliver tubular handling and running services that reduce flat time, manual handling and environmental hazards, while improving connection integrity and the capabilities of third-and fourth-generation rigs. And it is not just operators calling for such services in that country; after the 2010 Macondo oil spill in the Gulf of Mexico, Australian regulatory agencies such as the National Offshore Petroleum Safety & Environmental Management Authority (NOPSEMA) are calling for stricter safety and environmental controls on many offshore operations, including tubular management and running.
Weatherford has advanced its tubular management services approach to answer these requirements, by shifting these processes to onshore operating bases where better control and a more automated preparation strategy can be established.
Tubular management services comprise several key functions that are conducted dockside, including:
Pipe cleaning. Incoming tubular joints are received and cleaned onshore, using a pressure-driven cleaning unit and then dried internally with compressed air. This helps satisfy NOPSEMA’s environmental legislation that restricts the disposal of any waste into the sea, particularly around some sensitive locations such as marine parks.
Thread inspection. The thread protectors on each joint are removed and cleaned, and then threads are steam cleaned and inspected for defects or corrosion.
Drifting. Each joint is drifted from the box end with a nylon-bodied drift of appropriate OD. If the drift passes through the joint without binding, the operator is assured that the ID of the entire joint is sufficient to allow the drill bit to efficiently pass through it downhole.
Thread lubricant. Each thread is doped such that it is ready for field running, in accordance with client requirements, prior to reinstalling the thread protectors.
Pipe tallying. Each joint is laser tallied, and the length and size data are tagged onto it, either with a stick-on printed label or laser printed bar code applied directly to the pipe surface. This provides an extra level of assurance to the Australian operator that the pipe arriving at the rig site has been properly prepared and inspected from a quality assurance/quality control (QA/QC) perspective.
Accessory installation. If required, additional tubular accessories such as centralizers, float equipment or casing bits are installed per operator specifications.
Racking and transportation. The joints are installed in tubular transport frames or ‘wine racks’ for transportation to the rig. The packing order is recorded, with each joint being numbered and the pertinent data being recorded in shipping documents.
A recent advancement in tubular management services is the ability to make up doubles or triples – connecting two or three joints offline and off the rig floor – with the advent of bucking machines with associated torque/turn recording systems. One example of such a machine is an automated system (Figure 1) comprised of:
- A hydraulically operated bucking unit with 15in-diameter pass through and a torque capability up to 160,000ft lbf.
- A skid-mounted, electrically powered hydraulic power supply unit.
- A control panel with torque process controller and torque/turn recording system.
- Two single-joint pipe racks located either side of the bucking unit.
- A hydraulically operated, inclined tip/table for moving pipe joints from the single joint pipe rack to the pipe feeding facility.
- A pipe feeding system consisting of custom designed hydraulic jack stands to move pipe horizontally in and out of the bucking unit.
- A double pipe rack to receive made-up joints from the bucking machine.
The reduction in on-location, drill floor pipe handling has several advantages for an operator’s commitment to safety, environmental stewardship and operational efficiency:
Improved waste water management. Storage compounds for pipe joints must be washed off and replaced with a running compound prior to downhole deployment, which introduces challenges for the safe handling of waste fluids. Washing pipe offshore requires capturing the waste fluid and ensuring that it is not washed off the rig floor and into the sea. Onshore pipe cleaning, in a controlled environment, eliminates the risk of overboard discharge, significantly lowers transportation and disposal costs and allows for appropriate oil/water segregation and recycling.
Safety. In its 2011 Summary of Occupational Incidents report for the Asia-Pacific offshore region, the International Association of Drilling Contractors found that 36% of recordable incidents occurred on the rig floor, and 10% occurred on or near the pipe deck. This comes into clearer focus when one considers that space constraints on a rig floor force many operators to stack pipe five to six joints high. Thus when preparing pipe offshore Australia, rig personnel walking on the casing are working at heights of 1.5m or higher, which increases the risk of twisted ankles or falls.
Making-up pipe onshore allows for safer handling of pipe joints, and additionally, reduces the amount of rotary table (RT) activity on the rig floor. Further safety improvements are realized by the hands-free makeup systems afforded by tubular management services. Onshore pipe preparation can be performed under more controlled environmental conditions, such as under a canopy, to protect field personnel from the risk of heat stress that is common in the Australian summer, when temperatures can reach 50°C.
Improved logistics. Preparing the pipe offshore on the rig requires that it be there five to six days prior to running in the hole to allow sufficient prep time, which introduces deck loading issues and scheduling challenges for boats and crews. Prepping the pipe onshore at the yard avoids these logistics hurdles, and less activity on the rig floor helps reduce maintenance costs associated with rig floor machinery by reducing the number of connections made-up at the rotary table and extending the operating life of rig equipment. In addition, it reduces the number of days tubular running personnel are required onboard the rig to assist with pipe preparations, providing cost savings and reducing risk, particularly during Australia’s cyclone season when rig headcount should be kept to a minimum.
Further logistics and running time improvements are realized by prepping and moving doubles or triples to the rig, in a ready-to-run state. Running ready-made stands of doubles or triples also reduces running time, which translates to corresponding reductions in the amount of ‘open hole’ time. Further, it reduces wellbore conditioning and cleaning costs while enhancing safety, and rig time savings that reduce time to production. Similar savings are realized when shipping doubles or triples back to the shipyard for breakout into singles, rather than breaking them down on the rig. Given the high operating spread rates in Australia, even small time savings translate to significant cost savings.
Full inventory control and yard management. A subset of logistics benefits provided by tubular management services is the complete tracking of pipe inventory, down to the sequence in which it will be run in the hole. Each joint or joint multiple is tracked at every stage, from prep in the yard to downhole deployment.
With the level of QA/QC assurance provided by this service, a reduction in contingency tubular plans bring added benefits and cost savings.
Increased accuracy of pipe preparation. The use of tubular management services onshore allows for higher technology prep options to be deployed, such as laser measurement and barcode identification of each joint or stand, and drifting and strapping machines. Offshore preparation typically translates to more manual handling and preparation techniques, such as the use of measuring tapes and manual data recording. And a reduction in wellsite handling helps protect the integrity of expensive corrosion-resistant alloy tubulars.
Integrated operations. An operator can realize significant operational efficiencies by partnering with one provider to conduct both tubular management and tubular running services. Using the same company with the same employees that are multi-skilled and experienced in the comprehensive tubular running process ensures consistency and integrity in how the tubing is handled, controlled and run, and allows unforeseen problems with tubular management and running to be addressed quickly and correctly prior to wellsite installation.
Resultant improvements in rig efficiency using tubular management services have been documented in many locations, both on- and offshore. But given the high costs and risks associated with handling and deploying pipe for offshore wells, the most interest has come from offshore operators. This is certainly the case in Australia, where continued offshore E&P activity, and an increased emphasis on safe, efficient and environmentally responsible well construction operations in the last few years, has made tubular management a high priority.
A major operator working offshore in NW Australia and using a fourth-generation semisubmersible drilling rig wanted to improve its casing and tubing running efficiency by running doubles in a six-well program. The operator also wanted to improve safety and efficiency by reducing the manual handing of tubulars and bottomhole assembly (BHA) components. Previously, the operator had performed tubular preparation and make-up work on the rig floor, and was running only single joints downhole.
Weatherford was selected to provide management services that included mobilizing a bucking unit equipped with torque/turn process control systems to the operator’s onshore support base to make doubles of 95/8in, 7in and 41/2in PH6 tubulars. The operator also required full pipe preparation and yard management services (Figure 2). In compliance with these requests, the tubulars were cleaned, inspected and drifted; the threads were cleaned and doped; the tubulars were bucked into doubles, laser tallied and tagged; thread protectors were re-installed; and the tubulars were racked in double wine racks. They were then trucked a short distance to the quayside, where they were shipped to the rig.
The operator conservatively estimated that, when compared with earlier operations, running doubles prepared via the company’s tubular management services boosted handling efficiency by 30-43% (Figure 3). An average of four hours of rig time was saved on each tubular running operation by running doubles, which amounted to a total of 32 hours over the short campaign. At the hourly operating cost of US$52,000, this amounted to a savings of US$1,644,000 in operating expense, with a corresponding safety enhancement due to the reduced manual handling of the tubulars. The operator also calculated that a saving of $400,000 was achieved by preparing the pipe offsite, and eliminated the need for offshore pipe cleaning and transportation costs associated with wastewater disposal.
This same operator installed a top loading Hydraulic Mobile Bucking Unit (HMBU) on board the same rig for use in make-up and break-out of sub-assemblies such as hole openers, running tools and jetting tools for a separate six-well program. The HMBU recorded and stored the connection torque for the BHA, which improved connection reliability. In addition, by moving this activity off the critical path where it would have to be handled at the rotary table with manual tongs, the operator saved an estimated $6.9 million.
The use of tubular management services, particularly to run doubles in the well, can contribute substantially to improvements in operational efficiency and consequent cost reduction. This approach not only reduces overall operating costs, but can also have a major impact on HSE performance. It’s use should be a major consideration in the planning of any drilling and completion program. The recent successful deployment of these services offshore Australia is garnering the interest of other operators.