Unconventional reservoir

Unconventional reservoirsBy Basma Ahmed El-Sayed Supervised byProf. Dr. Abdel Moktader A. El-Sayed

What are unconventional resourcesUnconventional resources are hydrocarbon reservoirs that have low permeability and porosity and so are difficult to produce. Often enhanced recovery techniques, such as fracture stimulation or steam injection etc., must be performed, making the process more difficult than a conventional playGas- and oil-bearing shales are organically-rich, ne grained sedimentary rocks capable of producing commercially important quantities of hydrocarbons upon articial fracturing. These shales typically serve as the source, reservoir and seal of the hydrocarbons produced from them.

Conventional vs. Unconventional

Conventional ReservoirUnconventional reservoirContain gas can flow naturally and easilyLow permeability makes the flow is not easy Gas and oil is migrated from the source shaleGas and oil does not migrateThe reservoir rocks e.g.: 1-Sandstones2- Fractured limestones3-Fractured dolomiteThe reservoir rock is the source itself and has many types: 1- Shale Gas/Oil2- Tight Sands (TGS)3- Coalbed Methane (CBM)4- Tar sands5- Methane HydratesEasily production by direct methodTo produce from unconventional, we stimulate reservoir by creating a fracture network

Types of unconventional reservoir

Shale Gas and Shale Oil Tight Gas Sands (TGS) Coal Bed Methane (CBM)Tar sands Methane hydrate

Why do we need Unconventional Reservoirs?

1-Conventional sources are running out and the sources of renewable energy are not enough to fill in the gap of total energy demand. 2-Growing population and income per capital.3-Modern life depends basically on electricity and/or natural gas. Challenges :Groundwater contaminationWater sourcing and disposalInduced seismicity

Main Shale Gas Reservoir Characterization Depositional environment refers to marine or non marine shalemarine shales have lower clay content and are high in brittle minerals, such as quartz, feldspar and carbonates. brittle shales frac better during hydraulic stimulation.nonmarine shales deposited in lacustrine, fluvial environments, tend to high in clay content, more ductile and less responsive to hydraulic stimulation.

So, mineralogy of the shale samples determines how efficiently the induced fractures will stimulate the shale.

2. Thermal maturity measure of the degree to which a formation has been exposed to high heat needed to break down organic matter into hydrocarbons.

useful indicator is vitrinite reflectance (R); whether the rock has generated hydrocarbons and could be an effective source rock. prospective reservoirs have typical values ranging from 1 to 3% R

higher thermal maturity leads to the presence of nanopores, contributing to additional porosity in the shale matrix.

3. Total organic carbon (TOC) content Organic matter such as micro-organism fossils and plant matter provide the carbon, oxygen and hydrogen atoms needed to create natural gas and oil. TOC of prospective areas equal to or greater than 2%. An attractive feature of the shale gas reservoirs is its organic richness.

4. PorosityHow is gas stored in the shale reservoirs? As gas dissolved in kerogen. As gas adsorbed onto kerogen and clay particle surface. As free gas in natural fractures and intergranular porosity.

5. Permeability -The difference about shales is the matrix permeabilities of typical shales (the ability of fluids to pass through them) are very low (often termed ultra-low) compared to conventional low permeability oil and gas reservoirs-(nanodarcy 10-9 Darcy in shales versus millidarcy 10-2 in conventional sandstones) which means that hydrocarbons are effectively trapped and unable to flow under normal circumstances in shale.-Permeability is achieved through natural fracture systems or hydraulic stimulation. Storage is mainly in the matrix and the permeability is assured by the fractures.

6. Gas-in-place Governed by four characteristics: pressure, temperature, gas-filled porosity and net organically rich shale thickness. Pressure: areas of higher pressure are identified as they have higher gas concentration. (0.433 psi per foot: normal hydrostatic gradient). Temperature: A normal temperature gradient of 1oF per foot of depth is used. Gas-filled porosity: usually determined from cores and log curves.

Productionsweet spots:are defined as the most prospective volumes of the shale play. can be described as a formation volume that has the following characteristics:1- low water saturation with high TOC content and thence high kerogen content;2- low clay content and thence high brittleness index for fracturability;3- higher porosity;4- higher (effective interparticle) permeability; and5- low fracture initiation pressure preferably evidenced by natural fractures.

Elements of a successful shale gas play

How to produce shale gas/oil?Used technique :

Production worldwide

Production In EgyptEgypt has four basins in the Western Desert with potential for shale gas and shale oil: Abu Gharadig, Alamein, Natrun and Shoushan-Matruh. The target horizon is the organic-rich Khatatba Shale, sometimes referred to as the Kabrit Shale or Safa Shale, within the larger Middle Jurassic Khatatba Formation.

Thank you