Horizontal drilling gains traction

The boom in horizontal drilling presents new problems that require innovative solutions. Typical drilling problems such as stuck drill pipe have only become more acute with the emergence of horizontal drilling. Formation instability, improper hole cleaning and break-out debris in the hole wedged beside the drill string can cause drill pipe to become stuck resulting in costly pipe recovery operations.

The problem faced by operators is the conveyance of pipe recovery tools in the lateral section of a well if circulation is lost during the drilling process. Until recently, it has been impossible to reach a target depth in the horizontal section of the well with normal wireline techniques, since the method relies on gravity to convey the tools and cable to the target depth. This has left the operator with few options, the most common of which is time-consuming and expensive (CT deployment) or in the worst case abandoning the hole and side tracking.

Today, an alternative to the above two undesirable options is available. The necessary force to push a wireline toolstring through drill pipe and into the horizontal section of a well can be provided by using the Well Tractor. Operators are thus given the ability to convey pipe recovery and fishing services through drill pipe with an ID as small as 2.5-inches when gravity and pumping down are not possible or successful. These situations are usually the result of loss of mud circulation due to insufficient hole cleaning, which can then be followed by heavy mud settling, but also due to inability to pump into the formation.

In addition to drill pipe recovery services, MWD measurement cartridges can be fished reducing overall operational expenditures. The replacement cost of MWD tools is exceptionally high. By retrieving the MWD package, costs are greatly reduced. With rising service costs, it is crucial that operators execute fishing operations in the most efficient manner possible. The Well Tractor has fished MWD tools successfully at differing depths, inclinations, mud weights and drilling assemblies. Due to the Well Tractor’s design, it is well suited for driving inside drill strings and completions with changing IDs such as pipe connections, x-overs and landing nipples.

Fishing MWD tools in horizontal wells without fluid circulation

An operator in the Barnett Shale used the Well Tractor to retrieve an MWD tool. Pump down operations to fish the MWD were attempted but were unsuccessful due to a tight formation – the pump rate obtained was one-and-a-half barrels per minute at a 3000-pound pump pressure. Velocities required for pumping the tools down hole could not be achieved.

The Well Tractor was deployed and at approximately 70-degree inclination it was activated and tractored to a depth of 8500ft MD. At this point, pick-up weights were documented. The tool was re-engaged and tractored to a depth of 8950ft where its power supply showed a surface indication that the MWD was encountered and captured. The Well Tractor was shut-off and pick-up weights confirmed retrieval of the MWD tool.

Tractor time for 2190ft of the lateral section was an impressive one hour which is an averaged of 45ft per minute. Subsequent runs facilitated the re-establishing circulation and eventually the backing off of drill pipe. Total operating time for the entire fishing operation was less than eight hours and the customer was back to drilling.

Milling scale on wireline

A major North Sea operator experienced a build-up of scale in two gas wells. Traditionally this would have been removed by a method such as coiled tubing (CT), but in the case of these two wells, the costs were prohibitive. Instead, the Well Tractor was run in conjunction with the Well Miller to remove a total of 42ft of barium scale.

The result was that the field was able to export an additional four million cubic feet of gas a day. Furthermore, full access to the reservoir was re-established for future operations. The job was done in 12 days – the same time it would have taken just to rig up/down the coiled tubing equipment offshore.

Welltec’s technology takes less time to mobilise and deploy onto a drilling rig than other methods. It also recovers tools and conveys pipe recovery services through drill pipe more efficiently using electric wireline depth control. Finally, this technology requires less people and therefore less HSE risks to operations for overall reduced cost benefits.

About Jørgen Hallundbæk
Jørgen Hallundbæk is the founder, President and CEO of Welltec. Welltec’s flagship, The Well Tractor, was originally a part of Jørgen Hallundbæk’s master thesis from the Technical University of Denmark. In 1994, he founded Welltec and, since then, has created an international company with more than 500 employees worldwide.