Activities that Revolve Around the Development of Oil and Gas Resources

Exploration and Evaluation

This stage involves searching for oil and gas reserves. Since these reserves are deep beneath the earth's surface, locating them is not a child's play. One of the commonly used techniques is seismic. It helps identify the prospective fields. A part of the technique is seismic imaging. It measures the time taken by a signal to reach the receiver from the source. It also evaluates the signal's strength. On land, the source is usually a truck that generates sound vibrations. In the sea, it is an air gun that produces sound waves by releasing air bubbles in the water. After the sources release the energy, it travels through the subsurface rocks. These waves get reflected on the surface as echoes, which the receiver records. For this purpose, the land operators use geophones and the subsea operators' hydrophones. This data is then used to construct an image of the underground reservoir. In the initial days, the images were hard to study but now operators get access to 4D images. This helps them visualize fluid movements even in the well.

 Drilling

There are three types of drilling - vertical, directional, and offshore.

• Vertical drilling

After seismic imaging identifies the potential reservoirs, exploratory drilling confirms their existence. Onshore drilling operation uses drill string to cut through the layers of rock. The string creates a vertical hole called a well bore. This method helps identify reserves located directly beneath the drilling site.

• Directional drilling

For more than a century, vertical drilling has been largely used to find oil wells. However, the development of technology has offered another technique called directional drilling. Here, the well is vertically drilled to a certain point. Thereafter, an angular change gets introduced, can also be horizontal. Through horizontal drilling, one can retrieve around 75 percent oil in the reservoir. Also, it allows the drilling of additional wells without disturbing the existing wells.

• Offshore drilling

It refers to drilling operations carried in deep water. It involves drilling of wellbore below the seabed. Here, the drilling rigs are either floating or bottom-supported. The floating rigs include drillships and semisubmersibles. The bottom-supported category includes jack-up rigs and submersibles.

Recording of data

This step involves measuring the fluid and rock properties of the underground formations. Wireline equipment used to measure the data only after the drilling was over. Now, measurement-while-drilling techniques are in use. With their discovery, one can record real-time data while the well is being drilled.

Development and completion

When a reserve gets discovered, development and completion activities help tap the oil. It involves creating a path through which the oil or gas can reach the earth's surface from the reservoir. The first step involves casing the well. Thereafter, operators send steel pipes to the bottom of the well to collect the fluid.

Extraction