As part of a reservoir evaluation process an operator developing a new oil field in the Gulf of Mexico needed to measure the degree of fluid invasion during formation core drilling activities in order to accurately assess the amount of original oil in place.
The client contacted Tracerco to add one of their specialist oil based chemical tracers to the drilling mud prior to coring. This would allow the fate of the hydrocarbons within the drilling mud to be measured within oil extracted from core samples, and allow calculation of the corrected amount of oil originally within the core.
Tracerco worked closely with the operator and drilling fluid provider to select a suitable chemical tracer that would ensure there would be no safety or performance affect on the drilling mud following its addition.
Once proven, calculations for tracer concentration were made to measure core invasion of 0.2% or greater. Based on the drilling mud inventory, calculations showed 500 grams of material was required at a concentration of 10 parts per million.
Sampling and Analysis
A Tracerco Field Technologist was mobilised on site prior to the start of drilling operations through the formation zone of interest. The Technologist added the tracer into the drilling mud over one circulation period directly into the suction side of the mud tank. The drilling mud was then allowed to circulate for several additional circulation volumes prior to coring activities beginning.
Samples of drilling mud were regularly taken from the mud pit during coring and labeled with the date, time and depth.
Core samples were taken by a third party company, oil extracted from each, and a small amount sent to Tracerco. Analysis was carried out on each oil sample from both the core and mud samples.
Data was compared and the ratio between tracer within the mud and tracer detected within the oil extracted from the cores allowed the percentage invasion to be determined. A graphical representation of the data is shown below.
Organic phase of the drilling mud showed invasion levels up to 3.2%. Using this data the operator was able to better determine original oil in place across the pay zone. Tracerco offers both oil and water based chemical tracer technology for core invasion or bottom hole sample fluid contamination assessment.
For more information about Drilling Mud Core Invasion Measurement technology please fill out an enquiry form detailing your requirements and we will get back to you.