Better Drilling Through Chemistry

Better Drilling Through Chemistry

This entry is written by Debbie Thomas, co-chief scientist of Expedition 378. It comes from her Expedition 378 Odyssey blog, which can be found here.

Welcome to this special post featuring our night shift chemists (with glimpses of Ann from the day shift, of course)!

Are you ready to finally meet a real squeezecake? Behold….

A scientist is touching a squeeze cake with a metal spatula while it sits on a plate. The squeeze cake is a thick disc of sediment, about palm sized. There are several large grey instruments in the background - hydraulic squeezers.
Birthday girl, Blanca, successfully extracting the squeezecake from the squeezer…Tah dah.

Let’s journey back in time to understand how the squeezecake came to be. Recall the post We finally have CORE!! Now what?!. The shipboard chemists took a whole-round sample on the catwalk designated IW for interstitial water. Interstitial water is the fluid that exists between sediment grains, and we can learn important details about diffusion, biological and geological processes from downhole measurements of these fluids. The IW samples are carried downstairs to the Chem Lab (located on the Fo’c’sle deck) and prepared for loading into the squeezers:

A scientist manipulates a squeeze cake using two metal spatulas. Her back is to the camera and she is working intently. She is surrounded by hydraulic squeezers and large metal implements.
Eleni, renowned night-shift mischief-maker ;), scrapes off the sides of the sample that had been in contact with the core liner in order to load the cleanest possible sample into the squeezer.
A deep metal cylinder on a lab bench. A white sediment sample is barely visible beneath the rim of the cylinder. There is a muddy plate and metal spatula next to the cylinder - where the sample came from.
Sample safely loaded into the squeezer. Well done, Eleni.

After the squeezer is fully assembled, Eleni lifts it onto the base of the hydraulic press and begins the squeezing very slowly. There is a small hole at the base of the squeezer through which the extruded water will begin to flow. As soon as Eleni (or Blanca or Ann) notices the first drip of water emerging, she inserts the end of the syringe to begin collecting the fluid:

A scientist, Eleni, is looking up intently at the hydraulic squeezer. There is a metal cylinder and a plunger in the jaws of the squeezer.
Wait for it….

Eleni is holding a syringe up to a hole in the bottom of the squeeze cake cylinder. She is looking at the squeezer and smiling.
Boom! Happy chemist, happy co-chief/photographer.

At the other end of the chem lab, Blanca is weighing out dried and pulverized sediment for calcium carbonate analysis on the coulometer. One of the coolest innovations required to perform precise chemistry aboard a rockin’ and rollin’ research vessel is the ability to obtain the mass of the sample on a balance that compensates for the ship’s movement. Characterizing the amount of calcium carbonate in the core samples is one of the critical measurements needed to understand the overall composition and environmental conditions that existed at the time that these sediments were deposited.

A scientist, Blanca, sits at a lab bench full of machinery. She is scooping a sample from a glass vial. Her back is turned to the camera.
Blanca carefully weighs out a small amount of sediment powder for analysis on the coulometer (the collection of glassware to her right in which a small amount of acid reacts with the sample to determine the amount of calcium carbonate).

Other shipboard chemistry measurements on the pore fluids recovered from the squeezers include pH, alkalinity and sulfate, analyzed using the titrators located behind and to the left of Eleni in the photo below:

A wide shot of the lab. Eleni is standing at a lab bench lined with hydraulic squeezers. Behind her is a lab bench full of machines with glass tubes sticking out of the tops. There is a television mounted to the wall, and it is showing a grainy grey and red image of the rig floor.

You’ll also notice in the upper left corner of the photo the monitor of the rig floor – these are located throughout the labs and offices so that everyone knows the status of drilling and when to expect the next core.

The head space gas samples are analyzed using this gas chromatograph:

A large (mini-fridge sized) white instrument shaped like a box, sitting on a lab bench. There is a computer next to it and several boxes of glass vials and other chemistry equipment scattered around the lab.

The other type of pore water sampling performed on the cores involves drilling a hole into specified locations of the core sections and inserting a filter “straw,” called a rhizon, directly into the sediment. This enables us to target pore fluids from a narrower thickness of sediments rather than cutting an entire 5cm portion off the core to squeeze. Both strategies have advantages and complement each other in terms of the types of data we can obtain.

A scientist, Ann, standing at a wooden lab bench. There are two cores in front of her on the bench. Each has a tube in the plastic core liner with a syringe attached to it. Ann is holding one of the syringes and talking to someone off-frame.
Ann coaxing water out of the core and into the rhizon syringe.
In other news, Laurel and Ulla have implemented some defense strategies in case another core decides to SPLATter the correlator station:
A small figurine of a sailor with a pipe in his mouth and a blue shirt. The figurine's eyes have been covered by a piece of plastic that looks like safety goggles, and most of it is covered by a note card. The note card is folded around the figurine and "core blast shield" has been written on it.A small figurine of a girl playing a ukulele while wearing a grass skirt and flowers in her hair. The figurine has been covered by a folded note card that reads "core blast shield"

A tall rack with several white core sections resting on the shelves.
Come and take it, over-pressured cores….

Until the next time,

DT

23
Jan 2020
By Lindy NewmanGeochemistryLeave a comment

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