Xaminer™ Coring Tool retrieved 71 sidewall core samples in one run

Overview 

A great amount of planning is required for subsea well interventions. After a rig or intervention vessel is mobilized to location to connect the floating rig to the subsea wellhead with a marine riser, the subsea crown plugs must be pulled out of the subsea wellhead. When conventional slickline tools are unsuccessful in pulling the subsea wellhead plug, other methods must be used. Halliburton offers an extended-stroke downhole power unit (DPU®) tool capable of pulling subsea crown plugs when conventional methods fail. 

Challenge

This was an exploratory well drilled from a ship. Even though Halliburton had performed logging and coring services in the Santos area, it was unfamiliar with the properties of wells in this particular field.

Halliburton encountered a hard formation that produced very high wear on the bit. This resulted in poor core recovery. Halliburton collected only 24 and 20 samples respectively on the first two runs.

Solution 

To get a better feeling for the challenges it would encounter, Halliburton studied other presalt fields, then modified its tools, pressure settings, bits, and their configuration.

Halliburton suggested coring soft formations first, then coming back to harder formations. To get samples from those, Halliburton also suggested configuring the tool to collect 1-in. (not 1.5-in.) cores. 

Result  

On one run, Halliburton collected a world-record 71 large-diameter cores out of 72 attempts, more than doubling what it promised. This saved the client at least 24 hours of deepwater-drillship time valued at more than $1 million.

On the third run, Halliburton collected 71 samples from softer formations, a world record. On the fourth, Halliburton went back to the harder formation and collected enough 1-in. samples to satisfy the client’s need.