EXPLORATION DRILLING PRODUCTION AUGUST 2015

Transcription

1 EXPLORATION DRILLING PRODUCTION AUGUST 2015

2 COVER STORY PAT THORPEN & MARTIN SANDERS, LOGAN RENTALS, USA, EXPLAIN HOW NEW DOWNHOLE VIBRATION TOOLS CAN HELP OPERATORS OVERCOME THE OBSTACLES OF HORIZONTAL WELLS. F rictional drag. Stuck pipe. Sluggish hole cleaning. Worn drill bits. Extra trips. The list goes on and on. Historically, horizontal wells have created numerous obstacles for drillers, particularly in the unconventional shale plays throughout North America and across the globe. While several regions are exploring oil and gas production from shale formations and tight oil, according to the US Energy Information Association (EIA), only four are producing commercial volumes: the United States, Canada, Argentina and China. The challenges encountered with horizontal drilling become even more complex with extended reach drilling (ERD) in which the length of the horizontal section of the drill string often far exceeds the total vertical depth. As the horizontal distance continues to extend further and further away from the surface well site, it becomes increasingly difficult to maintain efficient forward motion of the drill pipe through the lateral. Excessive weight and torque placed on the drill string to make necessary directional corrections

3 Figure 1. Overall rate of penetration. The Xciter delivered improvement in overall ROP of 10.5 ft/hr (all wells, curve and lateral sections). Figure 2. Overall rate of penetration. Xciter performance gains in curve sections and lateral sections of 3.6 ft/hr and 9.3 ft/hr. causes both increased bit wear and damage to the mud motor from stalling/spudding events. The result is reduced bit life and an increased number of trips, which ultimately impacts the overall efficiency of the well. Due to the increasing length of the lateral sections, the drill pipe tends to rest on the low side of the wellbore, causing frictional drag and impairing the ability of drilling fluids to provide effective hole cleaning, both of which further slow the progress and efficiency of the well. All of these issues combined add up to reduced bit and tool life, lower average ROP and ultimately lower profitability. While extended reach wells offer huge benefits for the operator, such as maximising well productivity and reduced environmental impact from a singular pad-type drilling site, the extreme lateral distances amplify the hurdles the driller faces. Drilling increasingly longer laterals poses intrinsic complications that result in reduced ROP and overall cost-effectiveness of the well. Perhaps the greatest culprit is friction along the drill string when attempting directional corrections, which leads to stick/slip, buckling, lock-up, poor tool face control, lower differential pressure, motor stalling, high tortuosity, ECD fluctuations and more. As wellbore friction builds, forward motion of the drill string suffers, cuttings settle in the bottom of the wellbore, further increasing friction, which creates a vicious cycle of frictional drag and sluggish hole cleaning. Two types of downhole tools are generally employed to address friction along the drill string: axial oscillation tools (AOTs) and lateral vibration tools (LVTs). AOTs typically employ a valve driven by the mud flow to generate pressure pulses. These pressure pulses are converted to axial oscillating motions by a shock tool that is run above or as part of the AOT. The motion travels up and down the drill string to reduce friction between the drill string and wellbore. While axial vibrations can help reduce frictional drag 1, they have little or no effect on hole cleaning, and the jarring impact can cause more harm than good by damaging the MWD, interfering with signal transmission and drill bit wear or breakage. LVTs typically utilise a rotor and stator to drive an eccentric mass. The resulting action creates lateral vibration (perpendicular to the long axis of the tool) between the tool and the borehole to reduce friction in the BHA and along the drill string. The rocking motion created by LVTs induces enough energy in the BHA to reduce friction for more efficient sliding and rotating in the curve and lateral. The inherent advantages of LVTs over AOTs have been further enhanced with the introduction of Logan International s Xciter extended reach LVT. The tool utilises positive displacement motor (PDM) power to rotate masses of varying sizes, to excite the drill string with lateral vibrations. The motion introduced into the stagnant wellbore reduces or eliminates stick/slip, increases ROP, enhances tool face control and extends drill bit life. The Xciter tool is typically run one stand (or three singles) above the top Monel. The extended reach LVT is positioned close to the BHA, directly above the MWD, and is effective in all directional drilling applications (S wells, curve sections and lateral sections). As the driller reaches the bottom, the tool will use the bit as an anchor, and the vibrations resonate back up the drill string, allowing the BHA to more efficiently do its job. Because the tool creates a side-to-side motion instead of an axial up-and-down hammering motion, it is safe for MWD, LWD and EM, and does not cause signal interference. The extended reach LVT is added to the drill string when the driller begins the curve to further enhance slide and rotary drilling performance under the most challenging wellbore conditions. Running the tool in the build section helps produce more consistent curves and maintains build angles for smoother intermediate casing runs and more efficient lateral drilling. Proximity to the BHA enables direct impact and benefit to the sliding process as directional drillers are afforded more control over tool faces, differential pressure and weight on bit. This enhanced control allows drillers to orient much faster after surveys and hold more accurate and consistent tool faces while sliding to produce more efficient slides. As lateral vibrations induce movement in the drill string, the rocking motion helps to stir up cuttings that have settled on the low side of the wellbore, and stimulates slow-moving mud. Getting the stagnant cuttings integrated into the increased mud flow in turn promotes more efficient hole cleaning, which enables the drill pipe to move through the lateral with greater ease and efficiency. As the tool stimulates activity in the wellbore, drillers can expect minimal pressure drop, typically around 150 psi. Case study: the Powder River Basin The Powder River Basin, a region that spans square miles primarily in northeast Wyoming and southeast Montana, is well known for its abundant supply of coal, which is its largest natural resource. However, the Basin is also a substantial source of oil and natural gas, with ties to the industry as far back as The Powder River Basin experienced a lull in oil and gas production during the first decade of the 2000s, reaching a low of bpd. Experts attribute the slump to the previously uncharted territory of shale. Producers had tapped as much of the region as possible and stalled out because of the inaccessibility of resources deep within the shale plays. All that began to change in The development of directional drilling applications has made tapping these resources a reality and is largely responsible for the resurgence the region has experienced. According to the US EIA, production has jumped from bpd to bpd and more than 590 wells have been drilled since Increased production occurred in all six shale plays in the Basin, including the Shannon, the Sussex and the Frontier formations, which rose from 8900 to bpd. Nonetheless, the overall regional growth is heavily concentrated in the Turner, the Parkman and the Niobrara-Codell formations, which collectively increased from 4700 bpd to more than bpd in early The Xciter vibration tool has over 200 runs in this basin. A case study was performed on 25 wells from one operator in both the Parkman and Turner formations. These complex horizontal wells are approximately 7000 ft and nearly ft below the surface, respectively. Overall, (including curve and lateral sections), the tool delivered significant Reprinted from August 2015 Oilfield Technology

4 Figure 3. ROP and sliding efficiency. Sliding efficiency and overall ROP performance gains as a percentage of improvement over runs with no friction reduction tool. Figure 4. The Xciter improves sliding performance and allows more consistent build rates, resulting in less sliding footage per curve section. improvement in average ROP, achieving 42.9 ft /hr, an increase of 10.5 ft/hr over wells with no vibration tool (Figure 1). In fact, the tool demonstrated performance gains in curve and lateral sections of 3.6 ft/hr and 9.3 ft/hr (Figure 2). Sliding efficiency as measured by sliding footage per hole section improved 16% when compared to the slide efficiency of the hole section with no friction reduction tool in place (Figures 3 & 4). The tool s ability to orient quicker and hold tool faces more accurately allows more productive sliding, which produces more consistent and predictable build rates. The ultimate goal of virtually every downhole tool is to produce accurate, efficient results with as few complications and delays as possible in order to save time and reduce costs on the overall project, and increase profitability. Utilising lateral vibrations to reduce friction in the BHA and drill string produces smoother wellbore functionality due to accurate slides and reduced doglegs. The extended reach LVT is simple to operate, adjustable to match flow and mud weights, and is offered with the various common drill pipe connections found on any given job. With more than 5000 successful runs, the extended reach LVT produces more efficient slides enabling directional drillers to achieve the desired doglegs and directional corrections with less sliding footage. Reduced stick/slip and frictional drag, along with more effective hole cleaning, aids drillers in staying on target with continuous wellbore operations. These improvements help to extend the life of the bit, produce smoother curves and aid in achieving maximum horizontal distance, higher average ROP and reduced drilling costs. Reference 1. SPE/IADC MS Heisig/Wilson. Oilfield Technology Reprinted from August 2015

5 Reprinted from August 2015 Oilfield Technology