Petroleum Drilling & Well Completion - An Overview

Petroleum Drilling & Well Completion

Petroleum Drilling commonly comprises The Drilling Preparations consist of The Rigs type, Drilling Procedures and Engineering Challenges, the Aim, Conditions location, And Drilling Program, Location Accessibility, Tools and Equipment, then The Rigs Systems Elements And Proses comprises The Rotating System, The Hoisting System, The Circulating System, The Prime Mover, Pressure Control System. Drilling Crew and Personnel’s consist of The Rigs Operating Crew, The Support Personnel’s. Then Routine Drilling Procedures such Drilling A Head, Making Connection, Round Tripping, Formation Drilling Data, Well Logging Operations, and MWD, LWD & SWD.

Well completion means preparing the well for production, of course well completion is worded only when the well have sufficient amount of oil and gas to be commercially viable. In running casing and cement the initial cementing called primary cementing creates a sheet or cover of hard cement that fills the annulus space between the outside of casing and the well bore well. Its primary function is to block fluid movement and pressure transmission up or down and the annulus, subsequent cementing is called squeeze cementing, and it’s done to repair the primary cementing or in connection with a work over a well that is being rework because of declining production.

The Process of Running Cement

The process of running cement, first dry cement is mixed with additives made up of accelerators, retarders, and density adjusters. The function of these additives is to adjust the dry cement properties to fit the conditions of the well, accelerator speed up the setting time of the cement, retarders to the opposite they prevent premature setting in deep high temperature well. Density adjusters increase the cement weight to reduce pumping pressures or to permit a higher cement column without fracturing the formation.

After the casing in place, the cement is properly blended with water and the hole does prepared for pumping, first a hard rubber rupture plug is inserted into the casing followed by the cement slurry, this plug will separate existing mud from the new cement. Pumps to the bottom of the hole the cement slurry pushing the plug in front as it flows down forces the rupture plug into the seat in the float collar. Once in place the driller slightly increases the well pressure to break through this rupture plug. Once the plugs broken the cement slurry displaces the existing mud in the annulus, when adequate cement has been pumped a second plug called seal plug is then inserted. This seal plug serves the separate the cement slurry from the fresh mud that follows. Finally the cement slurry is displaced out of the casing into the annulus. The cement job was completed when the second plug the seal plug land in seats in the grooves in the floats valve, this landing is signal at the surface by a sharp pressure increase. The pumps are then shut down which allows the pressure to drop.

The decreasing pressure causes the flow valve to close preventing the heavier cement in the annulus from running back into the casing. After the pumps or shut down well operations or suspended for from twelve to twenty four (12-24) hours, so the cement can set.

PERFORATING

With the cemented casing in place the next task is to perforate the casing in the zone of interest, called the pay zone. Perforating mean blasting through the walls of the casing, the cement sheets and continuing on for about one (1) meter into the formation rock, it is through these holes that hydrocarbon fluids will pass to the surface when production begins (Pic. 44). To blast through the casing and cement jet perforator are set to 4-8 holes per foot, each shot is rotated ninety (90) degrees or one hundred eighty (180) degrees from the one above throughout the pay zone, to blast these jet perforators through the casing and into the formation, casing guns are used. The retrievable and reusable these casing guns are made of strong wing constructed steel which are run with an electric wireline.

Before first firing, the gun and the hole is filled with salt water. This salt water is called water blanket or load brine, when the well has perforated the water rush out through the new perforations killing the well and preventing a blow up. With the potential for further damaging the formation near the wellbore using over balance conditions the engineering team made decided to stop for the perforations until the world has been prepared for production. This means that the well will be outfitted with tubing packers and the Christmas tree there accommodate perforating in underbalanced conditions. In addition many of the subsequent well treatment processes described, then the next segment of this book are optimally done after the well has been outfitted with these three components, they include the wellhead and the various processes of preparing a well for production and will be discussed here. In preparing the well for production smaller diameter pipe, called tubing is installed down the casing with a packers at the bottom. Let we point out here that the permanent casing is rarely used as a conduit to get oil and gas to the surface. Remember it's main function along with the annulus is to seal the wellbore and keep it sealed.

TUBING

Instead smaller tubing installed through the casing is used to bring the fluids to the surface. Manufactured in joints a thirty (30) feet with threaded couplings the diameter of tubing can vary, depending the fluid amount projected to be produce. For example small tubing that is to and three eight 35 inches 2 3/8” outside diameter is used for shallow low productivity wells. While large six inch 6” outside diameter tubing is used in high volume gas well.

In any case tubing is smaller than either the drilling casing pipe and is relatively lightweight when compared to them, because of two the smaller size and weight it can be run in and out of the hole by work over rig out fit with small or a hoisting equipment when you would find any drilling rig.

Here you can see that these strings hang from the tubing hanger in the wellhead and irretrievable unlike the permanent casing strings. Keep in mind also that although only one set of casing is ever run tubing because of its smaller size can be run through the casing and single, dual or multiple strings.

CHRISTMAS TREE

Finally a Christmas tree is installed, containing valve manifold that controls flow in the tubing, they must be strongly constructed to contain full of reservoir pressure, a christmas tree function is to control the pressure. In the illustration, the main valves that control the well pressure or labeled, they are choke, master valve, crown valve, the wing valve, and the safety wing valve.

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References:

• Google.com
• Youtube.com
• https://www.amazon.com/PETROLEUM-DRILLING-OVERVIEW-Andi-Anriansyah/dp/1792194684
• https://www.amazon.com/PETROLEUM-WELL-COMPLETION-OVERVIEW-1/dp/1792195575