Corrosion
Corrosion is the deterioration of metals due to chemical reaction. Most common form of corrosion is through oxidization of metal surfaces. Most metals tend to lose electrons to oxygen in the air or in water. This process results in an oxide with the metal and cause deterioration of metal surface. When oxidation takes place due to different metal in contact with one another, it is called galvanic corrosion. Electrolytic corrosion takes place in electronic equipment when water or moisture gets trapped between two electrical contacts.
Tunnel
Once the well is drilled to the target depth and production casing / liner has been run, the well is perforated across the zone of interest for either testing or producing reservoir fluid. The term 'Tunnel' refers to the part of the perforation hole created by perforation guns in casing and cement. Part of the hole that extends into the formation is referred as 'Cavity'.
Shaped Charges
Shaped charges are used as part of testing and completion operations for perforating casing and formation. The charges are loaded on perforation gun and are lowered into the well either through wireline or drill pipe. Once on perforation depth, the charges are detonated through a detonating cord. The perforating jet formed as a result of explosion, penetrates the casing and deep into the formation. This creates a tunnel for reservoir fluid to flow into the well.
Shaped charges have four main parts; outer casing, premier charge, main charge and conical liner. Outer casing is the metal body that holds all other parts together. Ceramic or glass are also used as casing material. Premier charge provides the link between the detonating cord and the main charge. Liner is a cone shaped solid or powdered metalic layer that collapses under detonation pressure allowing the formation of perforating jet.
Detonating Cord
Detonating cord is a part of perforation set up. It is connected to detonator on one end and to the shaped charges of the perforation gun on the other. It is a means of transferring detonation from detonator to the shaped charges. Cord consists of high explosive core covered with plastic or lead jacket. It can have either round or rectangular cross section. Detonating cords are defined by grains per foot (gpf) which is a unit of explosive load per unit length. One pound contains 7,000 grains. Round detonators usually have 70 to 80 gpf.
Cavity Effect
Cavity effect refers to the effect of having a cavity in the shaped charges. Experiments indicated that flat explosive surface were not effective in achieving good penetration. When the surface was made with conical cavity, greater penetration was achieved. Experiments also revealed that having a conical liner as the front of cavity creates deeper perforations. Ability of shaped charges to perforate deeper into the metal and rock with conical cavity shape is termed as cavity effect.
Water Base Mud
As the name suggests, Water Base Mud is a drilling fluid with water as a base fluid.
Mud
Mud is another name of Drilling Fluid, which is a sticky mixture of various solid materials with liquid. Drilling fluid is continuously circulated while drilling in a close loop from rig's mud system through drill string, annulus and back to mud system. It performs various important functions and a properly designed mud system greatly contributes to the success of drilling process.
Drilling Fluid
Drilling Fluid also known as mud is a sticky mixture of various solid materials with liquid. While drilling, the drilling fluid is continuously circulated in a close loop from the rig's mud system through the drill string, annulus, and back to the mud system. It performs various important functions and a properly designed mud system greatly contributes to the success of the drilling process.
Bactericide
With time, the bacterial degradation of organic components of drilling fluid starts. It is usually detected through increase in carbonate alkalinity. Bactericide is a generic name for chemicals that are added to avoid bacterial degradation of the organic components of drilling fluid.
Yield Strength
Yield strength is the value of stress above which an irreversible plastic deformation would occur. All drilling tubulars have a defined yield strength based on the material used for manufacturing them. Yield strength is an important property which is used for selecting tubulars while designing a well.
Axial Strength
Axial strength is a function of cross sectional area of the tubular and Yield Strength of the material. It is calculated by the formula; Fy = π/4*(D2 – d2)*Yp. Axial Strength is an important factor while designing the well to determine the depth to which certain tubular can safely be run.
Trap
Once hydrocarbons are formed, they migrate upwards from the source rock. If this migration continues unabated, the hydrocarbon would eventually escape on the surface. Sub-surface accumulation is a result of the reservoir fluid hitting a barrier which doesn't allow it to migrate any further. This barrier is called Trap. It could either be a structural trap or a stratigraphic trap or a combination of two.
Tertiary
Tertiary is the period of Cenozoic geological era. In geological time scale, Tertiary period started around 70 million years ago and lasted till very recent time. Tertiary period had six different subdivisions called epochs. These epochs are Paleocene, Eocene, Oligocene, Miocene, Pliocene and Pleistocene in reverse chronological order from oldest to latest.
Terrigenous Sediments
Terrigenous Sediments, also known as Clastics are minerals formed from the fragmentation of silicate rocks. These are derived from land and are deposited following a sedimentary cycle. Clastics are categorized as Clay, Silt, Sand and Rudite based on the particle size.
Structural Trap
Structural traps are result of faulting or folding. It occurs when the migration of reservoir fluid is halted as a result of a non-porous formation blocks the flow due to shift of formations.
Stratigraphic Trap
Stratigraphic trap is said to exist when a non-porous formation seals off the top edge of a reservoir. The fluid in the reservoir rock migrates up as far as it finds good porosity and permeability and then stops at the non-porous formation. This phenomenon results in trapping the sub-surface accumulation.