Core Invasion Study

Westport Technology Center > Petroleum Geochemistry > Drilling Fluid Services

Core Invasion Study

Core Invasion Studies for Petroleum Geochemistry Reservoir Development and Management Services.

Core Invasion Studies
The goal of a core invasion study is to determine the amount of coring fluid contamination contained in the formation water of a core sample. Since contamination may affect the physical properties of the core and decisions about the future test program, the level of contamination must be known. In one type of study, a tracer, such as deuterium, is added to the coring fluid and the level of contamination is determined by measuring the level of the tracer in the extracted plug sample water. If tracers are not available, Westport has the additional capability of performing core invasion studies in the absence of tracers.

Tracer Studies
Westport generally performs tracer core invasions studies using a heavy water (D2O) tracer. In heavy water tracer studies, prior to coring, an appropriate quantity of D2O is added to the water-based coring fluid at the wellsite. During the coring process, periodic samples of the coring fluid are taken. When the core arrives at the laboratory, water is extracted from core plugs and/or trim using a Dean-Stark process. The levels of deuterium are then measured in the extracted water and coring fluid samples. Comparison of the tracer levels provides a straightforward method of determining levels of contamination in the extracted plugs. Westport can develop tracer studies using other tracers as well.

Tracerless Studies
When D2O, or other tracers, can not be made available at the wellsite, Westport can perform invasion studies in the absence of tracers. In tracerless studies, during the coring process, periodic samples of the coring fluid are taken. When the core arrives at the laboratory, water is extracted from core plugs by high-speed centrifugation. The samples are then analyzed for various cations and anions. The data are then examined using statistical techniques such as Principle Component Analysis and Multivariate Curve Resolution. The statistics are used to isolate the compositional variations that are caused by differences in coring fluid contamination. Once isolated, these variations can be employed to determine the level of drilling fluid contamination in the plug samples.