Completions and workovers are always undertaken with the hope that minimal formation damage will result and fluids will flow freely into the well. Too often that doesn't happen. Now a Canadian company is enjoying success with a mini drill that gently cuts short, radial laterals beyond the near wellbore.

In 1990, Grant McQueen with a silent partner and two employees formed Penetrators Canada, www.penedrill.com, in Red Deer, Alberta, to exploit a novel technology to rejuvenate wells in decline.
"We wanted to use a new jetting technology to get penetration beyond the near wellbore without adding to wellbore damage," said McQueen. "Everybody has seen wells stop responding to the usual recompletion and workover methods, or respond only for short periods, and then be abandoned with much oil still in place. There can be many causes for the decline, but most wells seemed to us to have problems in the near-wellbore region. Drilling fluids and cement invaded the formation, and produced solids clogged pores over the years."
The first Penetrators tool used high-pressure jetting technology and clear, lightweight completion fluids to cut several radial minilaterals. After creating a hole in the casing, the tool extended a hollow, flexible lance tipped with a high-pressure jet nozzle. The lance moved outward, and the fluid cut a tunnel up to 10ft (3m) radially into the formation. The technique was successful in some wells, but required expensive downhole equipment, special tubing and high-pressure pumps.
Though successes improved, job costs did not drop as equipment and high-pressure costs remained high. As they worked at it, the staff at Penetrators (now grown to 13) got the notion of replacing the jet nozzle and lance with a rotary drilling assembly and using a small diamond drill bit and a flexible drillstem. "It allowed us to get away from expensive high pressure and make the tool more efficient and capable while retaining the light and compatible completion fluids," said McQueen. In about a year, they completed design of a flexible, hollow drive shaft, drill bit and rotary motor to replace the lance and nozzle.
Dwayne West, who sells for Penetrators all over the world, tells of the first trial. "In June 1998, the PeneDrill Completion and Stimulation System as we came to call it drilled eight radial laterals into a thin-layered, oil-bearing Belly River sand with a water boundary in a Canadian Occidental well near Breton, Alberta. This was a region where the hydraulic tool had also been somewhat successful, and the performance and favorable economics of the new tool was immediately obvious."
Since the Belly River success, Penetrators has drilled more than 120 wells, and a picture of substantial benefits has emerged.
In Alberta's Utikuma field, drilling through the Gilwood (sandstone) at 5,676ft (1,730m), the PeneDrill tool was used to drill six radial minilaterals over an 8.5ft (2.6m) interval. Production, previously 94 b/d (15 cu m/day), stabilized at 182 b/d (29 cu m/day).
In central Oman, the PeneDrill tool was used in the Shuaiba limestone at about 4,593ft (1,400m) to open up formations that had suffered steep and rapid declines in injection rates after conventional perforating and acidizing (Table 1).