ABSTRACT
Radial jet drilling (RJD) is an unconventional drilling technique that uses the jet energy of high velocity fluids to drill laterals with different geometries in both conventional and unconventional reservoirs. Many case studies available worldwide have proven RJD as a viable alternative to traditional stimulation techniques, especially in marginal fields. RJD has a lot of application in the oil and gas industry. It is a cost effective completion technique to reach the untapped sweet spots, by-pass damaged zones near wellbore, re-complete old wells, and many other applications. The present paper outlines the basics of newly developed radial jet drilling technology. Advances in technologies, developments, forces imposed, jet fluid hydraulics, procedures, applications, and challenges of RJD are reviewed in this paper. Simulation studies and several worldwide case studies are discussed to evaluate the RJD technology.
Key words: Radial jet, drilling, completion, laterals.
Recently, the oil and gas industry has witnessed a steady increase in the use of short-radius horizontal drilling operations to enhance well productivity. The trend is expected to continue in the future as oil and gas industries become increasingly aware of the benefits associated with it while targeting thin reservoirs and oil reserves, which are pocketed and scattered. Horizontal drilling and new completion techniques have helped increase production in fields that may be uneconomic with traditional completions. However, these traditional techniques are still expensive and may not be suitable in marginal oil/gas reservoirs. Developing small and marginal fields with traditional techniques is expensive and economically unviable. For example, the cost can range from 1.0 to 10.0 million US$ to drill and complete one well. In addition, with increase in oil usage and demand, the need for finding new reserves has very high importance. Only new discoveries cannot compensate the rate of exhaustion of resources. As 60% of the world’s production is from matured fields, a better strategy to extend the production life of existing assets is crucial. Therefore new techniques, radial jet drilling, RJD, for example can be quite helpful in improving recovery, especially from marginal fields where the hydrocarbons reserves may not justify the high cost of horizontal drilling and hydraulic fracturing.
Abrasive water jet cutting of material involves the effect of a high-pressure velocity jet of water with induced abrasive particle. It is a recent non-traditional machining process, and is widely used in many industrial applications such as mining, shipbuilding, automotive, etc (Brooks and Summers, 1969).
The concept of water jet was first introduced in the 1960s and the initial applications were limited to cleaning and unblocking drains. With the development of new technology and availability of high-pressure pumps, water jetting gained importance and was used on commercial scale to cut soft materials such as cardboard and rubber. Many efforts were made in late 1960s to use water jetting in petroleum industry to drill sub-surface reservoir rocks, but favorable results could not be achieved because of deficient abrasive injection techniques (Birtu and Avramescu, 2012).
Drilling fluids pumped under ultra-high pressures can enhance drilling performance while maintaining conventional rig operating procedures and safety. The impact of the high velocity fluid stream can significantly assist the mechanical action of the rock bit allowing penetration rates of 2 to 5-times over conventional systems in comparable drilling conditions (Pervez et al., 2012).
Dickinson et al. (1993) reamed a large casing and pushed 1¼-inch coiled tubing between 25 to 150 ft (7.6 to 46 m) into formation for production enhancement (2 to 10 folds). Currently, RJD has been proven to enhance production rates, reduce decline rates, reduce near wellbore damage, and to recover more resources from stripper wells (Dickinson and Dickinson, 1985; Dickinson et al., 1990, 1993; Abdel-Ghany et al., 2011).
Radial Jet enhancement has made it feasible to enhance production from more than 1.7 million wells that would otherwise be cost prohibitive to recover. This represents a total potential untapped market of more than $50 billion. Using RJD technology, horizontal channels up to 300 ft (91 m) can be drilled out from an existing wellbore in any direction, with 1 to 2 inches (2.54 to 5.1 cm) diameter using high-pressure fluid. In North and South America, RJD technology is oriented toward existing oil and gas wells at depths of 4,500 ft (1372 m) and shallower for productivity improvement (Cinelli and Kamel, 2013; Kamel, 2016).
RADIAL JET DRILLING (RJD)
Abrasive water jet cutting is one of the non-traditional cutting processes capable of cutting wide range of hard-to-soft materials. Radial jet drilling is a process of drilling radials of small bending diameter horizontal perforations using water jets at very high pressure in different directions. The diameter of these radials is approximately 1 to 2 inches (2.54 to 5.1 cm) and lengths up to 300 ft (91 m). These radials can be drilled in multiple layers through same well (Figure 1). Abrasive water jet process includes large number of parameters, which affects the quality of cutting surface. These parameters include hydraulic pressure, traverse speed, stand-off distance, abrasive mass flow rate, abrasive materials, nozzle length and diameter, orifice diameter, abrasive shape, size and hardness (Ragab and Kamel, 2013; Patel and Shaikh, 2015).
This drilling process encompasses a wide variety of systems and concepts ranging from downhole tools to be added to a conventional rotary system to the use of surface pressure intensifiers with a parallel high-pressure flow path to completely new rigs designed specifically for jet-assisted drilling. Abrasive waterjet systems cut when the abrasive is accelerated above a critical velocity and the abrasive particles begin to chip out pieces of the target material upon collision. The higher the velocity, the more effective the cutting becomes (Al-Marahleh, 2015). When jet impact pressure and nozzle type is fixed, hole depth and rock breaking volume increases, and then decreases with the increase of standoff distance. The optimal standoff distance is 0.47 inch (12.0 mm) in the experiment (Wells and Pessier, 2003).
A simulation study was carried out on wells with different scenarios to accommodate a variety of reservoir permeability from high to low permeability values as shown in Figures 9 and 10 and forecasted an increase of productivity index with different number of laterals drilled as shown in Table 1 (Abdel-Ghany et al., 2011). As can be seen from these figures, the results show almost a triple fold of increase (FOI) in both high and low permeability formations. In addition, FOI depends on both number and length of laterals drilled. This confirms that RJD is a viable option for production enhancement.
Case studies
Case study #1: The Donelson West Field, USA
Cinelli and Kamel (2013) presented the case study of Donelson West Field, which contains 1,200 acres reservoir of limestone in Cowley County, KS. Its permeability is between 1.0 and 10.0 mD and its porosity is between 15 and 20%. The formation thickness is between 6 and 10 ft. The production history of this field can be traced back to 1968 where 13 wells produced a cumulative oil of 83,000 bbl. Afterwards, production declined quickly and in 1973, the cumulative production was about 15,000 bbl. Recently, the average production was about 1,000 bbl annually between the years of 2000 and 2009.
Development plan: Due to its declining history, despite of its high potential, a development plan was adopted in 2010 to stimulate the old wells and drill new ones. Eight old wells were reentered where laterals were jetted with RJD. In addition, two new wells were drilled and also jetted with RJD. After laterals were finished, all wells were hydraulically treated with equal quantities of acid and nitrogen. Afterwards, production started (Cinelli and Kamel, 2013).
Results: The two new wells with seven old wells showed a significantly improved production. The last well of the old ones did not show any production at all as it was drilled west of the field where the formation is normally very thin. Considering the low pressure, these could be the reasons why this well did not produce any hydrocarbons. However, production from the two new wells and the old seven wells was exceptional. A summary of the field production before and after the treatment is shown in Table 1. As can be seen, the monthly production bounced from 197 bbl, with an average production of 157 bbl before treatment to 1100 bbl, with an average production of 938 bbl right after the treatment.
Finally, and despite losing one well, the results show a significant effect of the treatment which confirms RJD as a viable alternative technique for production enhancement in old fields (Cinelli and Kamel, 2013).
Case study #2: Belayim Land Field, Egypt
The field is located in the central part of the Gulf of Suez, along the coast of the Sinai Peninsula and it is a multilayer field with separated reservoirs with interbedded shales and anhydrite intercalations.
Development plan: Radial drilling pilot tests were performed in three wells. In the first well (Well #1), 6 lateral drains were jetted at two main depths; three of them at 7460 ft (2274 m) and the other three were at 7450 ft (2271 m). Five laterals were 160 ft (49 m) long and the last one was 330 ft (101 m) long. In the second well (Well #2), 7 lateral drains, 160 ft (48 m) long were jetted with between 7650 and 7700 ft (2332 to 2347 m) depth. For the third well (Well #3), 4 laterals, 160 ft (49 m) long each were drilled; two at a depth of 7500 ft (2286 m) and the other two were at a depth of 8080 ft (2463 m).
Results: Well #1 showed an increase in production rate from 470 to 820 barrel oil per day, BOPD (about 350 BOPD gain) while there was no change in water cut. For well #2, RJD drilling was not as effective as in case of well #1. It only showed a slight increase in production from 233 to 246 BOPD. For well #3, there was no increase in production rate and this is believed to be due to the sand production problems. Well #3 has a history of sand production problems, which may plug laterals after being drilled. Well #2 and #3 were drilled in unconsolidated sandstone with a history of sand production and fines migration. This is one of the drawbacks of RJD, as it is not recommended for application in unconsolidated sand (Abdel-Ghany et al., 2011; Ragab, 2013).
Case study #3: K-block, Tarim Field, China
This is a condensate gas field producing since 1977 from a thin net pay of siltstone with low permeability and significant formation damage because of mud during drilling and completing operations.
Development plan: In 2010, a radial jet drilling plan was carried out to enhance the field production. The original pipe string was tripped out, workover operation was conducted, and then, RJD tools were lowered down to drill laterals.
Results: The data after RJD operations showed a significant enhancement in production. About 300% increase in oil production was obtained and even more, the field started to produce gas (Lu et al., 2014).
Further research
RJD, however, is a relatively recent technology in the oil and gas industry and still needs a lot of investigation and research to overcome its limitations and to explore new applications. For example, further research and testing of the jet nozzle penetration mechanism are required in order to identify the optimal nozzle configurations. New techniques are recommended to maintain the increase in production rate, especially in unconsolidated formation. Other areas for improvement from the author point of view include improved jet bits (most crucial), high strength materials and tubular goods, fluids and application of drag reduction concepts, alternative methods to clean laterals from cutting after jetting process.
Despite its limitations, RJD can be an effective tool for production enhancement and completions for both new wells and workover wells with radials up to 1,000 ft (305 m) long. It is a very viable, cost effective alternative for fracturing in marginal fields. However, candidate selection is a crucial parameter in RJD success. Petrophysical studies, in situ stress magnitude/distribution and rock cutting mechanics are necessary before well intervention to maximize benefits from RJD. In addition, further investigation is recommended to overcome RJD limitations and to explore new applications.
The author has not declared any conflict of interests.
Ai = Nozzle area
Ao = Hose inner area
C = Jet bit discharge coefficient
dh = Inner diameter of flexible hose
di = Inner diameter of coiled or straight tubing
do = Outer diameter of coiled tubing
f = Well friction coefficient
Fdf = Friction force between wellbore and deflector
ff = Friction factor
Ff = Friction force of well to high-pressure hose
Fj = Ejecting force generated by fluid jetting from nozzles
Fp-out = Fluids pressure on the forward surface of jet nozzle
Fpull = Pulling force of the high-pressure hose and the jet bit
g = Gravitational acceleration
lh = Length of the high-pressure hose
lt = Length of the coiled tubing section or straight tubing section
Pout = Ambient fluid pressure around the jet bit
Q = Flow rate
v = Fluid velocity in coiled or straight tubing
vi = Fluid velocity in the nozzle
vo = Fluid velocity in the hose
α = Correlation coefficient of deflector resistance
ΔPbit = Pressure loss through bit nozzles
ΔPCT = Friction pressure loss in coiled tubing
ΔPhose = Friction pressure loss in flexible hose
ΔPpump = Total pump pressure
ΔPST = Friction pressure loss in straight tubing
μ = Fluid viscosity
ρ = Fluid Density
ρh = Weight of high-pressure hose per meter
φ = Angle of the nozzle
Acrynoms
CT = Coiled tubing
FOI = Fold of increase
mD = milli-Darcy
BOPD = Barrel oil per day
REFERENCES
|
Abdel-Ghany A, Siso M, Hassan A, et al. (2011). New Technology Application, Radial Drilling Petrobel, First Well in Egypt. Paper OMC-2011-163 presented at the Offshore Mediterranean Conference and Exhibition, Ravenna, Italy, 23-25 March.
|
|
|
|
Al-Marahleh G (2015). Parameters Controlling Abrasive Water Jet Technology: Erosion And Impact Velocity For Both Ductile And Brittle Materials. IOSR J. Eng. 5(8):01-07.
|
|
|
|
|
Bin W, Li G, Huang Z, Li J, Zheng D, Li H (2016). Hydraulics Calculations and Field Application of Radial Jet Drilling. SPE Drilling & Completion. 2016 Mar 1;31(01):71-81.
Crossref
|
|
|
|
|
Birtu C, Avramescu V (2012). Abrasive water jet cutting-technique, equipment, performances. The Nonconventional Technologies Review. 15(1):40-46.
|
|
|
|
|
Brook N, Summers DA (1969). the penetration of rock by high-speed water jets. Int. J. Rock Mech. Mining Sci. Geomech. Abstr. 6(3):249-258.
Crossref
|
|
|
|
|
Bruni A, Biasotti H, Salomone D (2007). Radial Drilling in Argentina. Paper SPE-107382-MS presented at the Latin America & Caribbean Petroleum Engineering Conference, Buenos Aires, Argentina, 15-18 April.
Crossref
|
|
|
|
|
Cinelli S, Kamel A (2013). Novel Technique to Drill Horizontal Laterals Revitalizes Aging Field. Paper SPE-163405-MS presented at the SPE/IADC Drilling Conference, Amsterdam, The Netherlands, 5-7 March.
Crossref
|
|
|
|
|
Dickinson W, Dickinson W (1985). Horizontal Radial Drilling System. Paper SPE-13949-MS presented at the SPE California Regional Meeting, Bakersfield, California, 27-29 March.
Crossref
|
|
|
|
|
Dickinson W, Dickinson R, Herrera A, Dykstra H, Nees J (1992). Slim Hole Multiple Radials Drilled with Coiled Tubing. Society of Petroleum Engineers. doi:10.2118/23639-MS
Crossref
|
|
|
|
|
Dickinson W, Dykstra H, Nordlund R, Dickinson W (1993). Coiled-Tubing Radials Placed by Water-Jet Drilling: Field Results, Theory, and Practice. InSPE Annual Technical Conference and Exhibition Jan 1. Society of Petroleum Engineers.
Crossref
|
|
|
|
|
Dickinson W, Pesavento J, Dickinson W (1990). Data Acquisition, Analysis, and Control While Drilling with Horizontal Water Jet Drilling Systems. Paper PETSOC-90-127 presented at the Annual Technical Meeting, Calgary, Alberta, 10-13 June.
|
|
|
|
|
Elliott S (2011). Coiled-Tubing Method Drills Radial Lateral to Improve Oil Production from a Depleted Reservoir. NIOC Information Center and Central Library.
|
|
|
|
|
Gang B, Gensheng L, Zhonghou S, Zhongwei H, Dongjun M, Liangbin D (2013). Experimental Research on the Technology of Hydra-Jet Sidetracking of Radial Micro-borehole. Journal of Engineering Science & Technology Review. Nov 1;6(5).
|
|
|
|
|
Gensheng L, Huang Z, Tian S, Shen Z (2010). Research and application of water jet technology in well completion and stimulation in China. Petroleum Science. Jun 1;7(2):239-244.
|
|
|
|
|
Guo R, Li G, Huang Z, Tian S, Zhang X, Wu W (2009). Theoretical and experimental study of the pulling force of jet bits in radial drilling technology. Petroleum Sci. 6(4):395-399.
Crossref
|
|
|
|
|
Huanpeng C, Gensheng L, Zhongwei H, et al. (2013). Extending Ability of Micro-Hole Radial Horizontal Well Drilled by High-Pressure Water Jet. Presented at the WJTE-IMCA Conference and Expo, Houston, Texas, 9-11 September.
|
|
|
|
|
Kamel A (2016). RJD: A Cost Effective Frackless Solution for Marginal Fields. Paper SPE 184053 presented at the SPE East Regional Meeting, Canotn, OH, USA, 13 –15 Sep.
|
|
|
|
|
Kohar J, Gogoi S (2014). Radial Drilling Technique for Improving Recovery from Existing Oil Fields. Int. J. Sci. Technol. 3(11):159-161.
|
|
|
|
|
Marbun BT, Zulkhifly S, Arliyando L, Putra SK (2011). Review of ultrashort-radius radial system (URRS). InInternational Petroleum Technology ConferenceJan 1. International Petroleum Technology Conference.
Crossref
|
|
|
|
|
Patel K, Shaikh A (2015). The Influence of Abrasive Water Jet Machining Parameters on Various Response – A Review. Int. J. Mech. Eng. Robotics Res. 4(1):383-403.
|
|
|
|
|
Pervez T, Al-Hiddabi SA, Al-Yahmadi A, Seibi AC (2012). Dynamic Analysis and Vibration of Beam Inside Annulus for Ultra Short-Radius Water Jet Drilling. J. Eng. Res. [TJER]. 9(1):55-63.
Crossref
|
|
|
|
|
Ragab A (2013). Improving Well Productivity in an Egyptian Oil Field Using Radial Drilling Technique. J. Pet. Gas Eng. 4(5):103-117.
|
|
|
|
|
Ragab A, Kamel A (2013). Radial Drilling Technique for Improving Well Productivity in Petrobel – Egypt. Paper SPE-164773-MS presented at the North Africa Technical Conference and Exhibition, Cairo, Egypt, 15-17 April.
|
|
|
|
|
Lu Y, Li N, Zhou X, Wang X, Zhang F, Yang P, Yang C, Zhou B, Jin Y, Zhang T, Li J (2014). Radial Drilling Revitalizes Aging Field in Tarim: A Case Study. InSPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition Mar 25. Society of Petroleum Engineers.
Crossref
|
|
|
|
|
Wells R, Pessier R (2003). The Effect of Bit Nozzle Geometry on the Performance of Drill Bits. Paper AADE-03-NTCE-51 presented at the AADE National Technology Conference, Houston, Texas, 1-3 April.
|
|
|
|
|
Zhonghou S, Gensheng L, Ruihe W (1999). Current Status and Future Prospects of Water Jet Technology in Petroleum Engineering in China. Pet. Sci. Technol. 17(3-4):229-247.
Crossref
|
|
