New Analyses Indicate Bamaga Basin has Generated Natural Gas and Petroleum Liquids
Geochemical analysis of rocks from beneath the Gulf of Carpentaria has markedly reduced the exploration risk of Gulf Energy Pty Limited’s Q/23P project by confirming sediments in the Bamaga Basin have generated gas and gas liquids.
Fluid Inclusion Stratigraphic Analysis (FISA) was recently conducted by Schlumberger Technology Corporation on rock cuttings from the Duyken-1 well, located about 100km southwest of Q/23P in the Bamaga Basin, Gulf of Carpentaria. The analysesfound natural gas and gas liquids present as inclusions trapped in drilling cuttings at 450-600m depth in the well (refer to diagram below).
With this important information, and its knowledge of the geology beneath the Gulf of Carpentaria, GULF can draw the following exciting conclusions:
The hydrocarbons could not have been generated from the sediments drilled by Duyken-1 which are not sufficiently mature. They migrated from a deeper, more mature source and the only possible source is the Bamaga Basin beneath Q/23P.
Based on extensive experience, Schlumberger believe the inclusions, and the nature of their occurrence, indicates the gas and gas liquids migrated to Duyken-1 from another location.
This information markedly increases Q/23P’s prospectively and doubles its probability of exploration success from 1 in 9 to 1 in 4.
What is FISA?
Fluid Inclusion Stratigraphy Analysis (FISA) rapidly evaluates the entire borehole for the abundance, distribution, and composition of hydrocarbon and nonhydrocarbon types trapped in inclusions in drilling cuttings or core samples. Interpretation of results is based upon more than 25 years of experience and evaluation of several million samples—from virtually every depositional environment on every continent.
Results provide a depth-based view of the cumulative interaction of the five main elements of a petroleum system: source rock, migration, reservoir, trap, and seal. Evaluation of these fluids—which become isolated and confined within tiny cavities in mineral grains because of cementing and fracture ‘healing’ events—provides the mechanism for determining the present and past distribution of petroleum.
FISA benefits include:
Identifying migration and paleo accumulations in the absence of conventional shows
Evaluating causal relationships among rocks and fluids
Producing a regional picture of petroleum history
Anticipating the eventual perspectivity and distribution of emerging petroleum plays
The FISA technique involves mechanically crushing small core chips or small cuttings samples (0.5 grams of rock or less), followed by bulk analysis of evolved organic and inorganic fluid inclusion volatiles by quadrupole mass spectrometry using a rapid, automated sampling system, which allows continuous stratigraphic mapping of paleo fluids in the subsurface.
The study of over 20,000 wells worldwide has established the application of this technique in addressing petroleum charge and migration elements of risk associated with petroleum exploration and production.
Key indicator compounds and compound ratios are used to document petroleum migration through specific stratigraphic intervals, evaluate petroleum type and quality, and establish a time-integrated effectiveness for potential seals.
Additionally, FISA has proven proficient in identifying zones that are near reservoired petroleum, “proximity to pay”, even if that petroleum did not migrate directly through the analysed section. In these cases, water-soluble hydrocarbons, particularly benzene, toluene and/or organic acids occur in anomalous concentration and can often be shown to have migrated by diffusion through an aqueous phase away from known petroleum accumulations.
Basic Applications:
The technique has been applied in many different scenarios depending on the specific exploration, development or production problem being tackled. Some of the more common applications are:
Evaluate whether petroleum has moved through a dry hole with no shows that is adjacent to a prospect.
Determine whether oil or gas should be anticipated in an area
Infer the presence of a nearby oil field from a well with no hydrocarbon shows.
Investigate oil and gas occurrences from FISA data in relationship to source rocks in the study area.