With the estimated current supply of hydrocarbons in the United States studies have found that 41.5% of both oil and gas still remain above 3,000 ft (915 m). Shallow oil and gas wells from 250 ft to 6,000 ft (76.25 m to 1,830 m) have been drilled virtually the same way the last 140 years. The basic way to drill a shallow well up to this point has been to drill vertical and hope to hit a reserve. Hundreds of thousands of wells are out there today that have been drilled this way.
Horizontal Well Drillers has developed a new drilling rig designed to efficiently drill shallow horizontal wells with extended reach laterals. It gives operators a way to tap back into the reserves of old or orphan wells and produce new wells.
Horizontal wells generally increase productivity from four to as high as 25 times that of vertical wells. Wells that would have otherwise would have been considered marginal or uneconomical are now successful because of horizontal drilling. The following reservoir types are excellent examples of conditions that would benefit from this technology:
• Thin reservoirs where hydrocarbon deposits are wider than they are thick;
• Reservoirs with natural vertical fractures;
• Isolated and bypassed oil and gas reservoirs; and
• Reserves in environmentally sensitive areas.
True horizontal drilling can follow the pay zone on a flat axis up or down depending on formation. The problem with drilling rigs today is that when they try to go horizontal at
shallow depths, lack of penetration is encountered. Conventional drilling rig rate of penetration (ROP) is greatly reduced due to the lack of pressure that is exerted to the bit as
it is cutting.
Horizontal drilling today has the problem of going horizontal at a shallow depth. Some drill
|Figure 1. Drill site in Indiana. The rig is has a small footprint. Total jobsite size 200 ft by 200 ft (61 m by 61 m). (Images courtesy of Horizontal Well Drillers)
rigs can go horizontal but are limited to the footage horizontally. The bigger drilling rigs that are drilling 10, 15, and 20,000 ft (3,050, 4,575 and 6,100 m) deep can go horizontal much easier. The bigger rigs can go to lengths of 5,000 ft (1,525 m) horizontally and have no problems because they are so deep and are able to go off the weight of their drill stem. Shallow drilling rigs have a hard time going horizontal because there is a lack of weight behind the drill head to push horizontal. So it keeps the actual horizontal length very limited.
New drilling rig design
The design is state-of-the-art, compact, fast and cost-effective. The new drill rig can be built on a trailer or heavy transport that can be moved from site to site easily. The drilling rig is lying down flat when it arrives on site.
When on site the operator sets the rig upright by two hydraulic cylinders. The cylinders are mounted to the backside of the rig platform and to the trailer.
The drilling rig’s main design feature, which allows the rig to go horizontal with so much power, is the hydraulic rack and pinion system. Hydraulic motors move the drill stem up and down. The drilling rig has a push and pull rating of 500,000 lb. The design of the drilling rig was to make it very mobile. It can be set up and ready to drill in one day compared to two to five days with other rigs.
The main benefit is the increase in pay zone. With the longer laterals the pay zone can be as much as 108 times greater than conventional. The other major benefit is the lateral length from any depth. The rig is designed to go horizontal from depths as shallow as 250 ft down to 6,000 ft. The actual length of the laterals has gone to 5,000 ft (1,524 m), and plans are to go up to 7,500 ft (2,286.5 m) in the near future. Other major benefits include:
• Cost and time reductions;
• Increased safety;
• Steady ROP throughout the drilling process (80% at 5,000 ft). No major decrease when drilling at the end of lateral;
• Push and pull ratings of 500,000 lbs;
• Rotational torque up to 64,000 ft/lb depth rating of 15,000 ft (4,573 m) allows for use of 5-in. and 6 5/8-in. drill pipe;
• When drilling the rig uses one 5-in. drill string (does not need to use multiple strings of pipe);
• Lateral hole 8 3/4-in. is 44% larger than most 61¼8-in. conventional drillings systems;
• Mud pits are trailer-mounted and self-contained;
• Mud pumps and service equipment are all trailer-mounted;
• Very mobile — one day rig up/one day rig down;
• Low-cost mobilization — 10 load normal move;
• No casing crews;
• No lay down machines needed;
• While running casing the drill can rotate and circulate the hole;
• Tool joints will not hang up downhole;
• Safety — minimized roughneck assistance and 90% self automated;
• Enclosed mud cleaning system;
• One drilling rig from start to completion;
• Smallest foot print — 200 ft by 200 ft (61 m by 61 m) pad location; and
• Proven performance.
In June 2007 the company set out to do 10 test wells in Indiana. The area already had wells
||Figure 2. Rig is drilling down a rod and getting ready to load another. Rack and pinion system — the rig’s key design feature — can be seen.
drilled vertical on site years ago. The drill was set up to go the same depth as the existing wells and then go horizontal. The very first well was drilled and completed in 16 days. The lateral was 5,000 ft long. The next wells were drilled out and completed with laterals up to 5,000 ft in 14 days. Where it has taken three rigs in the past, we have done it with one. We are setting surface pipe and intermediate casing, and cutting the lateral while maintaining a high ROP. The wells that have been drilled out ranged from 400 ft to 700 ft (122 m to 213 m) deep with horizontal ranges from 4,000 ft to 5,400 ft (1,219.5 m to 1,646 m) in less time than established with the AFE. This has increased the pay zone exposure by as much as 108 times.
In addition to draining four to 25 times as that of vertical well bores, horizontal wells cost significantly less than drilling several vertical wells in the same area. The operating costs associated with infrastructure, wellhead equipment and maintenance is also greatly reduced. The performance of the new drilling rig has been excellent. The rig has completed wells far faster than anyone expected. With the drilling technology already proven we see the market as a whole changing from thinking drilling deeper to drilling known reserves with better technology.