We provide problem solving solutions, using geochemistry of rocks and fluids and petroleum system analysis (PSA), in exploration, appraisal, development and production for both conventional and unconventional settings – onshore and offshore.

Each project is customized to solving the main problem(s) defined by the client, and may include evaluation of existing data, design of a new sampling and/or analytical program, interpretations and integration with the geological and/or engineering models, presentations and reporting.

We could also work with the geoscience or engineering teams of the client and/or provide mentoring and training courses.

LIFECYCLE STAGES OF CONVENTIONAL VS UNCONVENTIONAL PLAYS

Play Audio– Conventional Plays

Play Audio– Unconventional Plays

Conventional Play – Lifecycle Stages

The lifecycle stages through which a conventional play goes through are Exploration-Appraisal-Development-Production. At the end, there is an Abandonment and Environmental Remediation stage.

The Exploration-Appraisal-Development-Production stages take place in a sequential order through time, and there could be a gap of few to over 10 years between individual stages, for example between exploration and appraisal or appraisal and development.

The Exploration-Appraisal are often referred to as “Green field” stages and the Development-Production – as “Brown field” stages. Note, also, how the scale of investigation changes from 100s to 1000s square miles at basin scale during exploration stage to less than 10-100 sq. miles during development-production stages.

During Exploration-Appraisal:

The focus is on the search and discovery of a commercial hydrocarbon accumulation, evaluating the size of the accumulation, type of fluids (oil vs gas) as well as fluid properties, which define quality and price of the fluids, and are used in the economic evaluation at appraisal.
Petroleum system analysis has a very important role and incorporates a continuous interaction between building the geologic model, basin model and using exploration geochemistry to evaluate main components of the petroleum system such as source rock, charge, migration, accumulation. Drilling an exploration well, which results in a hydrocarbon discovery, usually marks a transition to appraisal stage.
The appraisal stage involves drilling of additional appraisal wells to evaluate the discovery. During the appraisal stage, reservoir geochemistry may be utilized to evaluate presence of additional reservoir accumulations, fluid properties, in-reservoir processes (e.g., biodegradation, water washing, trap leaking, thermochemical sulfate reduction (TSR), that could alter fluid properties) and reservoir compartmentalization.

During Development-Production:

Additional wells are drilled to define the best way to produce the field and maximize the recovery of petroleum from the accumulation.
Petroleum system analysis still plays a role as the geological and basin models are updated with newly acquired well data but the role of building static and dynamic reservoir models becomes much more important.
The geochemistry applications, referred as reservoir and production geochemistry, become more important and could address issues such as reservoir compartmentalization, compositional graded fluid columns, prediction of water break-through, wax and asphaltene problems and remediation, operational issues.

Un-Conventional Play – Lifecycle Stages

Many of the basins with unconventional formations that started to be drilled and produced as unconventional resources, with the advancement of drilling and completion technologies in the late 2000s, have been discovered for a long time but they have been known mainly as source rock formations or tight reservoirs.

The Exploration Stage in such basins was completed as a conventional exploration play (e.g., Bakken, Eagle Ford, Marcellus shales).

The production in unconventional plays started, especially in the USA, with a very high rate of well drilling and completions by hydraulic fracturing (fracking). As a result, the development and especially appraisal stages were happening while the production was already underway.

The natural system becomes dynamic during production and a lot of the reservoir and fluid parameters change in comparison to their static condition – for example, reservoir pressure, reservoir temperature, gas-oil ratio (GOR).

In addition, it is unclear if any natural commingling of fluids occur from adjacent formations or zones prior to production due to the completion induced fractures that could reach lengths up to 100-300 ft. This presents challenges to building a reliable static model, which should be the basis for building a dynamic reservoir model, as well as to managing the assets efficiently long term.

The applications of geochemistry during these stages are a creative combination of exploration, reservoir and production geochemistry integrated with basin modeling results – for example, source rock and oil/gas characterization to evaluate the resource and STOIIP, identify sweet spots and guide geosteering of the wells, differentiate regions of oil vs gas dominant production, rock frackability, fractured zones, origin of non-hydrocarbon gases such as H2S and CO2, origin of produced waters, scale and environmental issues.

Surveillance applications of geochemistry involving monitoring of produced fluids as well as multi-disciplinary integration with drilling, completion and production engineering and reservoir characterization become especially important.

Conventional vs Un-Conventional Oil and Gas Resources

Conventional Oil and Gas – Oil and Gas Pools in which wells can be drilled so that oil and natural gas flows naturally or can be pumped to the surface at economic flow rates.

Uconventional Oil and Gas – unconventional oil and natural gas CANNOT flow naturally through the rock at economic flow rates, and requires special techniques to stimulate production (e.g., hydraulic fracturing).a

The term “Un-Conventional” simply refers to the methods that are used for recovery, as wellaas the types of rock from which the oil and natural gas are produced.

Sources: Alberta Energy Regulator, Unconventional Energy Resources, Petrowikia

Types of Unconventional Resources

Shale Gas, Shale Oil – natural gas and/or oil locked in fine-grained, organic-rich rock – Low Rock Permeability
Tight (reservoir) Gas, Tight Oil – oil found in low-permeability rock, including sandstone, siltstone and carbonates – Low Rock Permeability
Coal-based methane (CBM) – natural gas contained in coal – Low Rock Permeability
Heavy oils and tar sands – high viscosity oils and sands impregnated with bitumen (extra heavy oil) – High Oil Viscosity
Gas hydrates – a solid ice-like form of water that contains gas molecules, mainly methane, in its molecular cavities. Methane gas hydrate is stable at the seafloor at water depths beneath about 500 m.

Definition of Unconventional Resources based on Rock and Fluid Properties

In the 1970s, the United States government decided that the definition of a tight gas reservoir is one in which the expected value of permeability to gas flow would be less than 0.1 md. This definition was a political definition that has been used to determine which wells would receive federal and/or state tax credits for producing gas from tight reservoirs. Actually, the definition of a tight gas reservoir is a function of many factors, each relating to Darcy’s law.

Since low rock permeability (k) or high oil viscosity (µ) are typical for many of the unconventional type resources, definitions of unconventional resources have been proposed based on these parameters. Rock permeability is usually increased by hydraulic fracturing. High oil viscosity (µ) is usually reduced by heat (Candler, 2012).

Unconventionals have been defined based on rock permeability (k)

Unconventional resources have been defined based on both rock permeability (k) and fluid viscosity (µ)

According to the US Department of Energy (DOE), “unconventional oils have yet to be strictly defined.”

Production Enhancement due to Increase in Rock Permeability with Hydraulic Fracturing

The Role of Geochemistry in Petroleum System Analysis

Defining source rock (SR) characteristics and maturity

– Input SR parameters for basin models

– Calibration of results from basin models

– Integration with geological models

Defining petroleum charge and processes of:

-Petroleum Charge Expulsion, Migration

-Post-accumulation reservoir alteration (e.g., biodegradation, charge mixing, leakage)

By using fluid and rock geochemistry interpretations

CONTACT US TO FURTHER DISCUSS CUSTOMIZED SOLUTIONS TO YOUR BUSINESS ISSUES

Call Us: 713-898-9922
Email Us: ellie@ecgeochem.com