Stimulating for maximum recovery

Emerging out of the necessity to find alternative, less complex, and more precise stimulation methods, Fishbones was founded in 2004 by a Norwegian serial entrepreneur. The mission was to create a cost-effective, high-return stimulation method, with a lower CO2 footprint than traditional methods. This, in turn, would also open new markets for wells where other stimulation methods were not suitable, but where the wells had a potential for significantly improved production. Twenty years later, the firm finds that its technologies have become a logical choice in these markets. 

GAINING GROUND 

Based on operators’ diagnostics of the well, Fishbones’ technique allows oil and gas operators to target specific zones within the formation with pinpoint accuracy, removing reliance on formation stresses and strains. By mounting the Fishbones subs on the liner string to correspond to the zones where stimulation is to be carried out, the needles can extend laterally at the exact points where stimulation is most needed and most likely to succeed, Fig. 1. The lateral branches—resembling the skeletal structure of a fish—penetrate deep into the formation, effectively enhancing permeability and enabling the extraction of previously inaccessible hydrocarbons. 

Fig. 1. Fishbones’ needles can penetrate and connect reservoir layers to the wellbore by drilling or jetting laterally

Fishbones’ technologies were developed intensively by joint industry projects (JIPs), in collaboration with major E&P companies, since 2008, and they have gradually gained ground through a series of successful installations over the past 10 years. They have emerged as an attractive choice for operators seeking to optimize their production capabilities and to extend and improve oil recovery. 

The efficacy of Fishbones’ technology has been proven in numerous real-world applications across the globe. From the icy waters of the North Sea to the arid landscapes of the Middle East, Fishbones’ techniques have consistently delivered impressive results, developing a new approach to oil well stimulation practices and unlocking untapped reservoir potential. 

Three recent case studies are highlighted below, to show how the Fishbones needles have increased production many-fold. All of these case studies have been published previously in industry papers. 

DIGGING INTO LOWER LAYERS IN THE MIDDLE EAST 

Middle Eastern geologies are typically multilayered, with varying permeability. Reservoir quality can vary enormously in a single well, from productive high-yield layers to tight layers preventing vertical flow. Fishbones needles come in both drilling (Fig. 2) and acid jetting (Fig. 3) variants, and for the Middle East, the jetting needles are the most efficient in the prevalent carbonate fields. 

Fig. 2. The drilling needles come with turbine-driven drill bits.

Fig. 3. Jetting nozzles delivering simultaneous high-pressure acid dissolution with four jetting needles per sub.

In a Middle Eastern offshore horizontal well, dipping to sub-horizontal to sample lower layers, the prominent well characteristic was the difference in performance from upper to lower layers, where naturally producing fractures were present, and permeability was extremely low, Fig. 4. The operator was considering several options to boost production from the lower layers and to improve well performance.  

Fig. 4. A Middle Eastern offshore well was characterized by low production at lower levels. Jetting needles were deployed as part of the lower completion.

Possible solutions included matrix acid stimulation, drilling additional wells (stair-step horizontal or dual lateral) or utilizing Fishbones lateral needles. Before the final decision, successful lab-testing was done on core samples from the well, to assess whether the Fishbones jetting needles would be able to penetrate the samples, Fig. 5. 

Fig. 5. Lab testing of samples to determine penetration of acid jetting needles.

Fishbones was chosen over traditional stimulation methods, due to its capability for pinpoint stimulation to the lower layers. In the 4,085-ft (1,245-m) open hole, 20 Fishbones subs, with a total of 80 jetting needles, were deployed on a 4 ½-in liner across the two lower layers of the well. A successful deployment of the jetting needles, upon bullheading 3,000 bbls of 15% HCl acid, was accomplished, with needles achieving a deployed length of 1,684 ft in total. 

The result of the operations saw production from the lower levels boosted to 2,600 boed from the Fishbones-stimulated lower levels. The production increase was an astonishing 10 times the expected production increase of 250 boed. The well test productivity was increased by eight times, compared to the initial estimate of 1.5, while production uplift was increased by 10 times from 250 to 2,600 boed. The well continued to produce steadily at its new, increased rate. This well, alone, reached the production target of three planned wells in the area. 

SIX-FOLD INCREASES 

In another case study from the Middle East, a number of wells in an onshore, naturally fractured carbonate formation field were showing production rates well below expectations, due to low vertical communication between layers and low permeability. Additionally, low wellhead pressure was a concern. Average production was 200 boed to 400 boed, with 200 psi at the wellhead. 

The field, with several identical horizontal wells of 4,920 ft (1,500 m), was part of a series of field development projects in onshore fields to break boundaries and exceed expectations of production targets. Several wells were used for a comparison test by the operator. One well was selected for standard acid matrix stimulation, while another well was to receive Fishbones’ targeted stimulation with jetting needles. The wells were drilled in a multi-layered limestone reservoir with poor vertical permeability of 0.2 to 0.9 millidarcies. 

The Fishbones test well required 40 subs, with a total of 160 jetting needles, evenly spaced along the entire liner. The jetting operation achieved significant stimulation of the formation across the 1,500-m open-hole borehole. The initial five-day production testing period showed a 300% increase in uplift, with wellhead pressures stabilized at 400 psi, and the four-year period following the stimulation showed a sustained, six-fold increase in rates, confirmed by the production logging tool. 

Compared to the reference well treated with conventional stimulation, well productivity in the Fishbones test well increased 2.5 times, and the production rate was improved three times to 1,600 bopd, Fig. 6. The test well was the basis for a contract award of multiple additional Fishbones installations. 

Fig. 6. Performance and pressure comparisons of Fishbones well (green) compared to untreated well (olive) and acid matrix-stimulated well (purple). Graph from SPE-202636.

DRILLING THROUGH HARD CONGLOMERATES 

For two offshore wells on the Edvard Grieg field, on the Utsira High in the Central North Sea (Fig. 7), a different approach was needed. The challenge was increasing productivity in conglomerate formation wells for Swedish operator Lundin Energy, now acquired by Aker BP. 

Fig. 7. Fishbones drilling needles were chosen to penetrate the hard base conglomerate on Edvard Grieg field in the southern North Sea. Graphic: Aker BP.

Drill stem tests in the wells showed oil rates of less than 10 Sm3/d, and studies were initiated to evaluate various applicable stimulation methods. Hydraulic fracturing was ruled out, due to the geology not being beneficial for this method. Fishbones’ drilling needles were eventually chosen for their ability to provide controlled stimulation, with minimized environmental impact, during completion operations. 

The system was run as part of the lower completion with standard rig equipment, saving installation time and specialized vessel assistance. To penetrate the base conglomerate, 53 5 ½-in. drilling subs were deployed, generating 159 laterals. The drilling needles differ from the jetting variety, equipped with a compact ½-in. drill bit on each titanium needle. The specially hardened drill bits were developed in a JIP to handle the base rock, varying from hard granite to softer, unconsolidated textures. The drill bits were tested onshore in concrete blocks of varying hardness, containing 30% gravel of gneiss and granite, Fig. 8. The drill bits also had to be optimized for the especially abrasive drilling fluid. 

Fig. 8. To test newly developed drill bit prototypes, concrete blocks with added gravel of gneiss and granites were cast to simulate the hardness of North Sea base conglomerates

Upon deployment of the Fishbones system and completion of the lateral connections and production start, excellent results were recorded. Productivity was up multi-fold, compared to the original prognosis. The second well on the field, with 61 drilling subs, started production in January 2022, with a third well utilizing Fishbones drilling that was completed in August 2023 with 60 subs (180 laterals). 

IMPROVING AND EXPANDING 

Learnings from many years of development, testing and production have been unambiguous: using these lateral stimulation techniques gives operators enormous control over where, and to what extent, they wish to stimulate a well. While traditional fracing may achieve good results, control and predictability suffer, the effects may be adverse, and costs are often considerably higher than using Fishbones’ techniques. 

As a measure to improve oil recovery from unproductive or flagging wells, Fishbones excels as a stimulation measure. However, as we have matured our technology over the past 12 years since the first deployment, we have seen again and again why this technology should be an integral part of early-stage field planning and development. Integrating lateral drilling into the drilling or completions phase in wells with challenging or tight reservoirs from the start will ensure a better ROI over well lifetime, reducing emissions and increasing savings on platform time. 

In line with the ongoing energy transition, Fishbones is actively exploring opportunities in the conventional hydrothermal markets, particularly in Europe, where geothermal energy plays an increasingly significant role in helping to decarbonize the heating sector. We are also exploring applications in enhanced geothermal systems, e.g. in the U.S., further demonstrating the adaptability of our technology. 

Our expertise and proven track record in drilling and stimulation technologies has provided us with a strong basis for adapting to geothermal applications. Our technology and skills from oil and gas drilling and stimulation are transferable to geothermal. This adaptability makes it easier to explore and exploit sedimentary basins and reservoir sequences that are common in both oil and gas and geothermal fields. 

EXTENDING REACH 

While we can regard our technology base as sound and proven, we recognize that further enhancements can be made. In an ongoing collaboration with Aker BP, we are developing a new generation of needles. The goal is to extend needle length by 50%, moving from 12-m to 18-m needles, thus penetrating even further into the hydrocarbon-bearing formations to tap a reservoir’s recoverable reserves. This research on extended needles is also bolstered by a NOK 1.25 million ($117,100) grant from The Norwegian Research Council. We are, of course, proud of Fishbones being recognized in this context, as a company focused on reducing emissions by improving efficiency in the oil and gas industry. 

Proving the adaptability of our technology even further, we have developed a version of our needles with slotted apertures for use on the North Sea’s Valhall field. The slots will help in controlling loose chalk substrates on this field and prevent them from migrating into the well stream and to topside installations. 

We also have an ambition to provide even greater control of our needles in the future. A directionally controlled version is in development. This would allow even more accurate stimulation, if necessary. 

67 DELIVERIES TO DATE 

With 67 deliveries of Fishbones’ technologies, our approach offers a myriad of advantages over traditional well stimulation techniques, making it a compelling choice for oil and gas operators seeking to optimize their production capabilities and increase recovery. 

Additionally, operators can find compelling cost benefits by reducing the need for dedicated stimulation vessels, to perform the stimulation operation. The enhanced production rates facilitated by Fishbones' techniques translate into faster returns on investment, further bolstering its economic appeal. Combined with its minimal surface footprint, reduced chemical usage and reduced flowback volumes, we also see our techniques representing a progressive step towards a more sustainable resource development.