Primary seating and sealing is accomplished by the hanger in the bowl. This hanger grips the casing string and transfers the weight via the casing head shoulder to the first string casing and on to the ground. The casing hanger sits here when the casing is landed, now this does not necessarily mean that the … Continue reading Casing Head & Baseplate (Pt. 2 of 2)
The casing head represents the base of the wellhead assembly, it begins the transition of the wellbore from sub-surface casing to surface/topside infrastructure. The casing head is often attached to the first casing via threaded or slip on and welded connection. The head will be critical in supporting the weight of the wellhead and production … Continue reading Casing Head & Baseplate (Pt. 1 of 2)
The process is typically divided into 2 stages, the pad and the slurry. In the first stage the slurry is injected into the well to break down the formation and thus create the pad. At this stage the fluid injection rate is greater than the rate at which the fluid can escape the formation. The … Continue reading Fracking (Pt. 2)
This is the process whereby the fissures and existing cracks within a geological formation are expanded and enlarged by the application of pressure. The process seeks to increase the permeability of fluid bearing rocks so as to increase the flow of the fluids through it. The process is employed within the oil and gas sector … Continue reading Fracking (Pt. 1)
Short Normal The usefulness of the curve will be determined by the vertical resolution. The short normal (SN) is useful as long as the contrasts between the drilling fluid and formation resistivities are not too great. Resistivity beds will appear thinner by the arm spacing (16ins.), and conductive beds appear thicker by the same amount. … Continue reading Short Spaced Resistivity
Measures the natural resistivity of the formations in the borehole. Good for the identifying lithology and correlation purposes. The GR log usually reflects the shale content of the formations because of the concentrations of radioactive materials in the shales/clay. Shale free sandstones and carbonates have low gamma ray values unless contaminants are present. They are … Continue reading Gamma Ray
Spontaneous Potential (SP) This is a record of the direct current voltage differences between the naturally occurring potential maintained by a movable electrode in the borehole and a fixed potential located at the surface. The potential is as a result in the difference between the salinity of the drilling and formation fluid. The SP log … Continue reading Spontaneous Potential (SP)
Sonic Log Essentially it emits a sound pulse and has a receiver that picks up the sound pulse as it passes the receiver. This produces a transit time and generates a wave form that can be interpreted. In the sonic log the velocity of the wave form through the rock matrix will help to determine … Continue reading Porosity Logs
Facies A body of rock with specific characteristics. Defined on the basis of colour, bedding, composition, texture, fossils and sedimentary structures. Facies Sequences A sequence of facies as the pass from one to another. The sequence can have an abrupt or erosive boundary or a hiatus. In this case there is a coarsening upward sequence … Continue reading Sedimentary Environments
The Principle of Uniformity This states that the processes operating today affecting the earth have been operating unchanged at the same rates throughout the earth’s history. Relative Time The occurrence of a geological event relative to each other. This helps in the dating of geological occurrences. It helps with the identification of a geological continuum. … Continue reading Geological Time
Introduction There are three types of rock types that are studied when considering the geological environment. They are no particular order: Sedimentary Igneous Metamorphic The circumstantial evidence has suggested that hydrocarbons that are formed and deposited are strongly associated with sedimentary rocks. They are the result of altered organic material derived from microscopic plant and … Continue reading The Oil and Gas Story
The reasons are as follows; To support the vertical and radial loads applied to the casing Isolate porous formations from the producing zone formations Exclude unwanted sub-surface fluids from the producing interval Protect casing from corrosion Resist chemical deterioration of cement Confine abnormal pore pressure Cement is introduced into the well by means of a … Continue reading Why Cement (a wellbore)?