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Frac Sand Cleanout
Recent horizontal drilling methods coupled with multi-stage fracturing has allowed E&P companies to access massive amount of resources from low permeability shale reservoirs. The initial productivity of these wells has been impressive; however the decline rate and intervention frequency is higher than anticipated. Many of these issues are initially attributed to premature artificial lift failure due to solids abrasion or plugging, as well as abnormal productivity declines.
Generally, these reservoirs have been stimulated with hundreds of thousands of tons of proppant. This proppant, when placed into the formation improves the ability of oil and gas to enter the lined section of the well. However the primary fracture at the formation “sand face” can have low closure stresses at specific areas. A second contributor to this problem is specific to open hole packer liner systems. The proppant in in the area between the outer diameter of the liner and the inner diameter of the borehole and between the packers does not have any closer stresses on it. As the oil and gas flows through this low stress and annular area it can carry proppant into the liner of the well. Seismic events can also contribute to sand movement from the above listed conditions. All of these conditions allow proppant to move from a radial permeability matrix in the reservoir to a linear ultralow permeability matrix in the liner. Further, the velocities of the fluid and gas in the liners of these wells are not adequate to carry all of the inflowing proppant to the artificial lift pump and in most cases these pumps cannot produce the proppant to surface. This proppant then accumulates in the liner creating a very low linear permeability matrix, oil and gas cannot flow through it, this has become an impermeable solids bridge that stops or significantly reduces production from all intervals below this depth. This is where the JetVak system excels.
Quantum’s JetVak ™ system offers E&P companies a unique solution to not only remove these impermeable solids bridges but to simultaneously gather valuable inflow properties from the reservoir during the same operation. With its patent-pending design, which includes Dual Coiled Tubing and a modified jet pump. The JetVak™ uses a venturi to create a localized drawdown in the well while being cycled into the well. The venturi vacuums the wellbore debris and artificially lifts it to surface, circulation is guaranteed. Conventional cleanout methods such as tubing bailing, swabbing and conventional coil circulation are not as effective, dynamic and efficient as the DCT JetVak™ system.
Through our case histories it has been proven that wells cleaned with the under-balanced JetVak system produce at a higher daily rate, decline at a lower percentage and run trouble and intervention free for an extended period of time.
The JetVak can provide accurate data regarding what is being pulled from the wellbore, what each zone is producing (oil, gas, sand, water), which zones are depleted, and which zones need re-stimulation.
Quantum can not only clean the entire wellbore, but also the surrounding formation. This can break down the formation skin, resulting in a higher permeability area surrounding the production casing.
Sand bridges, which close off the downhole side of the wellbore from the wellhead, are given special care to make sure that all of the sand is removed to prevent continual build-up. The source of the problem is located and also taken special care of, typically the nearest downhole port.
Produced Sand Cleanout in CHOPS Wells
Cold Heavy Oil Produced with Sand (CHOPS) wells are prolific as high sand cut wells, which is inherit in the name. It is a fantastic design for production as sand needs velocity and viscosity in order to remain in suspension. However, oil flowing through the ports creates a bottleneck that will squeeze sand out of suspension. In addition, any deviation in the drilling will create low spots which are an initiation point for sand to not only fall out of the oil, but to build up and slow flow. Often this results in a solid bridge across the wellbore, which will deny any further oil from being produced past that point.
CHOPS wells have relatively poor recovery numbers, so any drop in fluid flow efficiency has a large impact on overall production. This leads our clients to demand a wellbore that won’t limit the capability in any shape or form. With the patent-pending JetVak system, our on-site technicians will be able to determine problem areas with high sand cuts and remove all blockages.
Quantum’s post-cleanout examinations typically see a high initial production directly after cleaning, but more-so a flat production curve that requires less maintenance in the future. This is due to not only having a clean wellbore, but also the near-wellbore area has capacity to attract sand and not reduce permeability. With a longer lifespan, capital expenditure is reduced in the long-term, not just immediately.
The modern oilfield has become a hotspot of technology, and Quantum Downhole Systems is a forerunner in investigating downhole situations. Our Q-Vak production evaluation system can accurately investigate the downhole conditions of any wellbore. This gives substantial insight in to the composition of a well on a zone to zone basis. Knowledge that identifies each thing allows producers to make educated decisions on how to treat each well for maximum perfomance.
Typically the Q-Vak is ran after a JetVak cleanout in order to have a clean slate in which the variable of wellbore conditions is removed. This ensures precise and accurate data is obtained: bottom hole pressure, temperature, return rates of oil, sand and water. This can be compared to the coiled tubing data to get accurate location where these properties occur. Assuming a stable flow rate from the well is established, a quantifiable IRP curve can be created for the well.
A new technology in Quantum’s arsenal of downhole evaluation tools is TAM International’s coiled tubing expandable packer system. This assures specific zone isolation to quantify the production and drawdown characteristics of individual ports.
Drilling Damage Removal
Drilling a wellbore is a deliberate disturbance of a formation’s mechanical characteristics. Drilling mud is selected on a multitude of parameters; these include preventing formation fluids from entering into the well bore, keeping the drill bit cool, migrating cuttings to surface. However, the near-wellbore area is often damaged to the point where production suffers from a loss of permeability. In the exploration and production business, there’s only two important points: the total invested capital in a well, and how many barrels it produces.
Reservoir rocks are water-wet in nature. It has been demonstrated that while drilling with oil-based mud systems, excess surfactants in the mud filtrate that enter the rock can cause wettability reversal. It has been reported from field experience and demonstrated in laboratory tests that as much as 90% in production loss can be caused by this mechanism. Although the surfactants are not very far-reaching in to the formation, all it takes is a pressure drop across the damaged skin to reduce the overall well production.
The JetVak system creates a far-reaching pressure drawdown that can remove the formation damage which inhibits production. It doesn’t matter if the damage comes from clay swelling, excess surfactants creating a water-wet substrate, mechanical blockages from formation fines, or a combination of multiple sources.
Liner Failure Cleanout
Liner failure is an increasingly common problem, especially in older wells. Without proper maintenance an unintentional perforation can occur in an unknown location downhole. This is evidenced by an unusual amount of foreign solids (such as sand or even liner debris). A direct indication of liner failure is sand and metal filings returning to surface when vacuuming the wellbore. Quantum’s on site experts will analyze the returns and accurately find the failure. This allows the client the ability to decide upon the appropriate repair method, whether it is to simply isolate or fully scab the liner where the failure is located.
SAGD or Steam Flood Cleanout
Bitumen (both mined and from wells) made up 80 per cent of Alberta’s oil production last year, and SAGD accounted for 52 per cent of the bitumen produced from wells in 2013. Another 23 per cent came from wells using cyclic steam stimulation (CSS), and 25 per cent was from wells that don’t use steam, according to the Alberta Energy Regulator’s 2014 reserves report, ST98-2014. While SAGD is an incredibly high production method, the technology used to monitor steam pressures and temperatures require large amounts of maintenance. The wellbore is no different.
Although SAGD and CSS are very similar in theory, they are very different in practice. Not only in operations with steam flood having two wellbores and CSS using one, but in the geology of the reservoir. SAGD only works well in reservoirs that have high vertical permeability, such as Grand Rapids Formation, Clearwater Formation, McMurray Formation, etc. With high permeability comes opportunities for fines to moves freely throughout the depleted areas and enter the wellbore, especially when being encouraged by steam.
Where Quantum excels in SAGD cleanouts is the ability to precisely monitor which ports are producing sediment and focus on these troubling areas. With standard swabbing efforts, a large scale sweep is performed, whether an area needs cleaning or not. The JetVak system is able to stay in a trouble zone until all blockages (both in the well and in formation) have been brought to surface. This results in a producer well that will run trouble-free for years.
Cyclic Steam Stimulation Wellbore Cleanout
Steam stimulation methods have been implemented since the 1970s, but only in the past 20 years has this technology gotten a foothold. With any flowing bitumen, a certain level of solids will be trapped in the viscous medium. These often fall out of solution in the wellbore where the cross-sectional area is much greater than the flow channels in formation. Although the initial recovery cycle works well, further cycles often bridge off the wellbore. Even when the sand does not create a fully impenetrable barrier, it often reduces the area available to flow, and therefore the production suffers.
Quantum has multiple case histories of cleaning out CSS wells which were suffering in their 2nd, 3rd, 4th cycle. All of these wells came back on much stronger than previously expected, some stronger than the initial cycle. While reservoirs get depleted when they are produced, Quantum’s patent-pending JetVak system clears not only the wellbore, but also the surrounding formation skin. This higher permeability reduces the pressure drop seen in all wells from reservoir to wellbore. CSS wells typically have lower bottom-hole pressure when they are off the steam, which plays right in to the JetVak’s hand. The closed hydraulic circuit works at any pressure, and specializes in under-pressured wells.
Source Water Well Reservoir Development
Source water wells have become more prevalent with the increase in steam injection wells in Western Canada and internationally. However these wells have remained on the lowest end of priorities for E&P companies as it is “only” water, and production is not a critical as the oil producing wells.
This is a fair mindset when considering the overall economics of an operation, but larger than an underdeveloped water reservoir is the premature degradation of the pumps used to bring the source water to surface. The Electric Submersible Pumps (ESP) that are landed in these wells are very susceptible to wear from formation fines travelling with the source water. Whether the pump is a 20 m3/day trickle pump or a 200 m3/day fire hydrant, sand tears through the impellers and opens flow channels that will kill a pump months ahead of planned maintenance.
Quantum’s advanced JetVak system pulls sand not only from the wellbore that has accumulated below the pump, but also the fines that are near the casing that will follow fluid flow to the pump shortly after the workover. Special attention will be given to the client’s needs, and a program will be developed to create the exact cleanout envisioned. Whether that involves cleaning extra sand from the formation around the pump area, or staying on a spring location for longer than usual, Quantum strives to deliver the best possible results every job.
Injection Well Cleanout
While many substances have been injected in to wells over history, they have all been done so with the same purpose: to enhance recovery. With enhanced oil and gas recovery typically comes enhanced solids and water recovery. These choke off the flow of the desired product. Injection wells typically go through a cycle from a producer to an injector and vise-versa, which causes problems on both sides of the equation.
When a producer sees a drop in production, this can be caused by a multitude of reasons. If a sand bridge occurs mid-lateral, the production drop will be noticed immediately and a depleted reservoir can be to blame. E&P companies can make an excellent educated decision to flip the producer to an injector, but this sand bridge will stop injection to every zone past this blockage.
Where Quantum excels in injection cleanouts is the ability to precisely monitor where along the lateral blockages occur, and the composition of returns to surface. If a sand bridge is tagged and cleaned, Quantum’s on-site experts monitor what returns to surface on the other side of the blockage to determine whether injection attempts have been successful. In addition, Quantum may employ a 4-nozzle jetting Spincat to effectively clear liner perforations.
With standard swabbing efforts, a large scale sweep is performed, whether an area needs cleaning or not. The JetVak system is able to stay in a trouble zone until all blockages (both in the well and in formation) have been brought to surface. This results in an injector well that will run trouble-free for years.
Drilling Fluid Cleanout
In the early days of drilling, both vertically and directionally, drilling mud was a simple water-based solution designed to mitigate formation damage and break down quickly & easily. However, with the advent of polymer-chain based drilling fluids, downstream production facilities are seeing problems reducing and separating these proteins.
When wells are drilled it is often seen that drilling fluid remains in formation, especially if the formation is under pressured. Typically there is a drop-off point where everything (oil, water, drilling fluid, etc.) from this point to the toe doesn’t flow back to the wellhead. Quantum’s patent-pending JetVak system works in every condition, especially with low bottom hole pressure. Our case histories have documented a large increase in Estimated Ultimate Recovery (EUR) in wells that are cleaned out immediately following drilling when compared to offset wells in the same pad. On-site experts monitor returns throughout the job and when drilling fluid is discovered, extra attention is given to make sure that returns are clean reservoir fluid is flowing to surface before continuing.
Multi-Frac Ball & Seat Milling/Cleaning
One of the newer developments in the hydraulic fracturing industry is the ball-drop system. While it gives great isolation from lower zones in the initial treatment, retrieving these balls has proven difficult and often they remain in the wellbore while fluid is returned around them. This has been mitigated somewhat with dissolvable balls, however these too can sometimes remain in the wellbore. In addition to the balls being problematic, the seats (which remain landed in the wellbore) often plug up with sand once production is started. The combination of these obstacles in the liner create a very hydraulically inefficient flow path for the produced fluids to come to surface.
The industry standard approach is to mill these wells out. In Q1 of 2015, Quantum Downhole Systems created a brand new milling design which uses concentric coiled tubing to separate the motor power fluid from the returns energizing fluid.
This revolutionary design allows the head to be independently controlled when the milling gets tough, while circulation is maintained with minimal fluid usage. Once the well is cleaned of all the balls, seats, sand, etc. and the mill has landed at the toe, the mill head can be decelerated to maintain rotation and circulation fluid can be increased.
Quantum Downhole Systems is continually committed to technologies that will allow field operations to run efficiently and economically. This includes taking proven oilfield technology and implementing value-added designs.
In early 2015, Quantum developed the capability to separate the fluid that energizes the circulation of milling debris from the fluid that powers the milling motor. With the dual coiled tubing used on every job and an innovative BHA connector, the Dual Coiled Milling System was created.
Since the forefront of the assembly is standard milling tools, it has the capability to attack the most challenging wells that the oilfield has to offer.
However, it achieves the same results with less fluid used and the capability to vary lifting rates throughout the wellbore, regardless of the mill head speed. This includes dropping the fluid sent to the motor while running out of hole, but ramping up the N2 (or other fluid) to ensure that the wellbore does not have residual milling debris left over