Tools of the trade

Weatherford’s Alex Goodwin explains how a RFID circulation sub displaced seawater to facilitate a formation integrity test in the Gulf of Mexico.

The JetStream circulation sub can be activated using RFID tags or pressure cycles for added operational flexibility. Photo from Weatherford

A unique application of a drilling circulation sub enabled an operator in the Gulf of Mexico to perform a formation integrity test (FIT) on a casing shoe in a shut-in well. The well had been cased 17 years prior to the operation; however, upon drillout, a FIT indicated poor isolation between the 22in and 26in casing shoes. The operator installed two cement plugs, but opted to abandon rather than cement the well.

After 17 years, the operator had reason to believe that barite sag and formation collapse may have increased shoe integrity in the abandoned well. Because of the degree of uncertainty, however, they did not want to invest in a high-pressure wellhead housing (HPWHH) and riser. The operator therefore sought an alternative way to perform a FIT.

Weatherford proposed using an inflatable packer as a barrier to keep the well static during operations. To implement this unusual technique in an offshore well, Weatherford also needed a method to precisely spot fluids to control fluid dynamics during and after the test. Weatherford selected the JetStream RFID circulation sub, which is normally deployed during drilling operations, to manage fluid displacement.

The rig crew deployed the JetStream sub, set the inflatable packer, and completed the FIT test without incident. A drillpipe plug was then set above the packer and below the JetStream using wireline. The large, full bore of the JetStream sub made it possible to run wireline through the inside diameter (ID) of the sub and set the plug below the sub and above the packer.

The plug-packer combination served to protect the wellbore in two ways. First, the plug prevented drilling fluids from entering the area of the wellbore below the packer, which was extremely sensitive to pressure changes. An influx of fluids into this area could potentially fracture the formation and compromise the FIT test — thereby jeopardizing the main objective of the operation. Secondly, the packer helped to prevent seawater from entering the open hole. The presence of seawater in the open hole would have increased the risk of well-control issues, especially considering the shallow water flow in the field.

After setting the plug, the crew needed to activate the JetStream sub to displace seawater from the annulus to the drilling fluids above the packer. The JetStream sub is normally actuated using RFID tags, but in this case the plug would have prevented RFID tags from flowing through the tool. Instead, a Weatherford field specialist used pressure cycle activation — a method in which a series of pressure pulses are sent downhole in algorithm-determined intervals — to open the tool. The seawater was displaced from the annulus to above the sea floor. With the ports open, there was sufficient flow to pump down RFID tags and close the JetStream using RFID actuation.

Fluid dynamics were carefully monitored throughout the operation. After closing the JetStream sub, the team detected an underbalanced condition, which was remedied by re-opening the sub to displace additional fluids. Once balance was restored, the team closed the JetStream sub and retrieved the plug and packer using wireline.

As a result of this operation, the operator obtained reliable FIT data that confirmed the integrity of the casing shoe prior to investing in a HPWHH. With the integrity confirmed, the operator is proceeding with plans to continue drilling the well.

While it is unlikely that many operators will find themselves in this identical situation, the project showcases the level of operational flexibility that can be achieved using advanced downhole tools. The large, unobstructed ID of the JetStream sub, along with its ability to be reliably actuated via pressure cycle, made it well-suited to overcome the specific challenges presented by this job.

Alex Goodwin is the global business development manager for performance drilling tools at Weatherford. He is responsible for supporting technologies including the JetStream RFID circulation sub, the RipTide RFID drilling reamer, and Dailey Jars in the US, Canada, and Trinidad. He holds a bachelor’s degree and an MBA, both from Louisiana State University.