There are many different methods to increase the efficiency of oil & gas wells production that along with progress and expansion of science have under gone changes and development. Radial Jet Drilling is a technique which utilizes hydraulic jet energy of fluids to drill lateral holes inside the reservoir.
At present time in Iran, the rate of production has decreased due to over extraction. Using new methods such as Radial Jet Drilling (RJD) would be more effective to increase rate of production instead of drilling new wells.
This method (RJD) has been used in case of oil reservoir with high porosity and permeability for many years.
- Fluid Jet Drilling
In 1950, Norman Franz, who was an engineer, used primitive method of water jet in cutting lumber. This method didn’t develop until Mohammed Hashish used a new method by adding some abrasive material to water jet. These days water jet is the only method in many aspects of cutting. There are different types of water jet such as simple water jet (without any additive), water jet with abrasive material, impact water jet, water cavitation jet and hybrid jet.
Spraying a stream of fluid with high velocity and pressure, is useful in different industries. Using water jet is common in metal industry, drilling, grinding and polishing stone. This method is used in cutting stones in case of decorative stone industry and construction. However drilling with water jet method is known for a long time but recent advantages in manufacturing nozzles causes increasing production.
In this way, fluid, often being water or abrasive particles mixed with water under high pressure is pumped through the coil tubing into the well. The fluid is ejected out from nozzle drill head at high pressure, wears out the stone resilience, and thus, drilling is done.
In some cases, the water pressure is not used alone in the drilling, but the drilling technology is used along with adoption of other methods. For example, in directional drilling, a method of causing detour in the well is fluid jet.
Drilling with fluid jet, includes wide range of methods and plenty of research have been carried out in this area. For example, we can use the jet of carbon dioxide, abrasive material or variable pressure of water jet. Very high pressures such as 20,000 to 60,000 pounds per square inch (psi) is used in cutting pieces of stone with water jet. But in normal drilling, water pressure is about 3,000 to 10,000 pounds per square inch (psi) respectively.
- Radial Jet Drilling Method (RJD)
RJD method is one of the very environmental friendly and economically feasible technologies that makes high-volume drilling achievable. The drilling in horizontal and vertical direction is done in different levels. Ramifications are done in mother well in different directions and levels, in exploring for oil or gas.
- RJD Technology
RJD is a drilling method which utilizes coil tubing conveyed drilling to create micro diameter holes by expending the energy of high velocity jet fluids. A small section of casing of the mother well is cut and then lateral holes are drilled in desired direction.
The hardware used in this method are: bottom hole assembly consisting of casing cutter, small diameter bit, orienter, steering tool, controller, coil tubing unit (3 1/2” , 2 1/8”) which is used to convey the drilling process from the surface, two mud pumps and 100 flexible hose. Experiments show that the deeper theholes, the more efficient the wells. The lands containing consolidated stones have shown better results rather than non-consolidated stones in this way. It is necessary to carry out soil mechanics studies and tests before RJD operation. Maximum operating depth is approximately 3000-4000 ft and a maximum operating temperature is 248 ° F. In higher temperatures, hose will be damaged. The fluid properties depends on the fluid used in the method and ingredients as well as the rocks and geology. The most common fluid is water, but when the fluid reservoir is in the form of wax, it would be better to use diesel fuel.
- Procedure of the operation
This way, whether on land or sea, requires drilling machine style (500-1000 hp). Drilling process is as follows:
- Drilling rig is transferred to the well station.
- Equipment and well completion equipment must be removed from the well.
- Coil tubing 2 1/8 “or 3 1/2” with deflector shoe that is mounted at the end, driven into a well and gets in the desired location. At the top of the deflector shoe, gyro determines the direction of the hole.
- Size of mobile tubing which is based on the well can be 5/8 “or 1”. The process should create same radial size of driller (1 3/4 “) with flexible hose and drilling for making the hole in line with the desired direction.
- Pull out mobile tubing from the well. Flexible hose (special) with a nozzle that is fastened to the end of the coil tubing is driven into a well.
- According to figure, hose enters into the hole and flow is pumped through tubing and flexible hose with 3,000-10,000 psi pressure. Drilling hundred meters with the pressure of the fluid will be available for two hours. For the second injection, it is possible to widen the hole to 4 inches.
- Bring out mobile tubing with flexible hose from well. Change shoe direction according to the requirement by rotating tubing. To create a new hole, the same way is done again.
In pulling up process out of hole, it is possible to inject acid with different concentration to increase production according to reservoir engineering. Usually four holes (possibly more) is drilled in four directions. This technology does not have a good result in falling layers.
If the hose was stuck in the hole and was not possible to take out, hose should be cut to stay in the well and other holes should be drilled without stopping.
The required time for well operation is 5 days by considering 2 hours for each hole and bringing out coil tubing (2 1/8” or 3 1/2”).
Operating cost is estimated about 300,000 to 350,000 $. Experience has shown that in some of the wells, the efficiency increases by 3 times.
- Advantages of RJD
- Create and increase reservoir seepage channels
- Connect natural gaps to each other and therefore possibility of faster drainage
- Small and large scale fractures formation around the hole
- Deep acidizing possibility in directional fractures
- Remove barriers around wells and the area around it
- Communication between the preceding perforations and new district
- Increased efficiency of operation with combination of acidizing and hydraulic fracturing
- Extension of the discharge area of each well
- Reduction in the flow resistance by increasing evacuation radius
- Increase in the radius of the practical effects such as acidizing, nitrogen injection, CO2 injection and intended solvents
- Better access to high gain points of well
- Available multidirectional jet drilling at different depths
- Improvement in permeable formations without harming structure
- Improvement in geo-mechanical operating efficiency and also sensitive directional operations
- The applicability of usage of various chemicals and fluids as the working fluid jet
- Alternative to friction layer
- A method for controlling layer friction and other chemical injection or steam
- Easy usage of this method at perforation
Also in this method it is possible to create holes in directional and horizontal angle by changing the angle of the deflector shoe, but not to create vertical hole.
One of the most important points that the oil industry is facing today, is the pollution caused by drilling oil wells. With proper management and implementation of appropriate requirements, the amount of pollution could be reduced.
One of the solutions is to use the radial drilling with fluid jet that can sometimes increase production up to three times and is a step towards improving efficiency in production.
Ms. Process Engineer