Fig. Schematic of example rig circulating system

 

The mud pump draws in mud through a suction line from the mud pits, or tanks, and sends it out a discharge line. From the discharge line, the mud goes into the standpipe. The standpipe runs vertically up one leg of the derrick. Mud exits the standpipe into a strong, flexible, and reinforced rubber hose called the rotary hose, or kelly hose. The rotary hose joins the swivel at the gooseneck. The mud then flows down the kelly (or through the top drive), drill pipe, and drill collars. It jets out of the bit nozzles and moves cuttings away from the bit. The mud and cuttings then head up the hole in the annulus. The annulus, or annular space, is the area between the drill string and the wall of the hole.

The mud leaves the annulus through a steel pipe called the mud return line. It falls over a vibrating screen, the shale shaker. The shaker screens out the larger cuttings and, in some cases, dumps them into the reserve pit. Offshore and in environmentally sen­sitive areas, however, the shaker dumps the cuttings into a receptacle. Later, the contractor removes the receptacle, washes the cuttings if required, and properly disposes of them. In either case, the clean mud drains back into the mud tanks. The pump then recycles it back down the hole. The mud pump recirculates the mud over and over throughout the drilling of the well. From time to time, the derrickhand adds wa­ter, clay, and other materials to make up for downhole losses. This crew member also adjusts the mud's properties as the borehole encounters new and dif­ferent formations.

 

 

Time to drill

The crew sets up and starts the drilling operations. First, from the starter hole, they drill a surface hole down to a pre-set depth, which is somewhere above where they predict the oil trap is located:

1. place the drill bit, collar and drill pipe in the hole;
2. attach the Kelly and turntable and begin drilling;
3. as drilling progresses, mud circulates through the pipe and out of the bit to float the rock cuttings out of the hole;
4. add new sections (joints) of drill pipes as the hole gets deeper;
5. remove (trip out) the drill pipe, collar and bit when the pre-set depth (anywhere from a few hundred to a couple thousand feet) is reached.

Once they reach the pre-set depth, they must run and cement the casing – place casing-pipe sections into the hole to prevent it from collapsing in. The casing pipe has spacers around the outside to keep it centered in the hole.

The casing crew puts the casing pipe in the hole. The cement crew pumps cement down the casing pipe using a bottom plug, cement slurry, a top plug and drill mud. The pressure from the drill causes the cement slurry to move through the casing and fill the space between the outside of the casing and the hole. Finally, the cement is allowed to harden and then tested for such properties as hardness, alignment and a proper seal.

Drilling continues in stages: they drill, then run and cement new casings, then drill again. When the rock cuttings reveal the oil sand from the reservoir rock, they may have reached the final depth. At this point, they remove the drilling apparatus from the hole and perform several tests to confirm this finding:

· well logging – lowering electrical and gas sensors into the hole to take measurements of the rock formations;

· drill-stem testing – lowering a device into the hole to measure the pressure, which will reveal whether reservoir has been reached;

· core samples – taking samples of rock to look for characteristics of reservoir rock.

Once they reached the final depth, the crew completes the well to allow oil to flow into the casing in a controlled manner. First, they lower a perforating gun into the well to the production depth. The gun has explosive charges to create holes in the casing through which oil can flow. After the casing has been perforated, they run a small-diameter pipe (tubing) into the hole as a conduit for oil and gas to flow up the well. A device called a packer is run down the outside of the tubing. When the packer is set at the production level, it is expanded to form a seal around the outside of the tubing. Finally, they connect a multi-valved structure called a Christmas tree to the top of the tubing and cement it to the top of the casing. The Christmas tree allows them to control the flow of oil from the well.

After the rig is removed, a pump is placed on the well head. In the pump system an electrical motor drives a gear box that moves a lever. The lever pushes and pulls a polishing rod up and down. The polishing rod is attached to a sucker rod, which is attached to a pump. This system forces the pump up and down, creating a suction that draws oil up through the well.

 

starter (hole)	начальная \ первичная скважина
pre-set depth	предварительная глубина
attach (v) [kelly]	установить (ведущую трубу)
float (v) [rock cuttings out of the hole]	удалить (шлам из скважины \ вымывать шлам из частицы, выбуренной породы)
remove (trip out) [drill pipe]	извлечь (бурильную трубу)
run and cement the casing	эксплуатировать и цементировать обсадную трубу
spacer	распорка (промежуточное кольцо)
bottom plug	нижняя (цементировочная) пробка
cement slurry	жидкий цемент \ глина
alignment	выравнивание \ регулировка
oil sand	нефтеносный песок
perform tests	проводить тестирования
confirm (v)	подтверждать
well logging	каротаж
take measurements (rock formations)	произвести измерения (горных пород)
rock formation	формация \ геологический горизонт
drill – stem testing	апробация бурильной колонны
device	механизм
core sample	керн \ образец
perforating gun	пистолет - перфоратор
production depth (level)	глубина залегания пласта
explosive charge	взрывной заряд
packer	трубной пакер \ сальник уплотнитель
multi- valved structured	много- клапанная структура
christmas tree (x-tree)	фонтанная елка \ фонтанная арматура
gear box	коробка передач
push (pull up and down)	поднимать \ спускать
polishing rod	полирующий шток (глубинной насоса)
sucker rod	насосная штанга
suction	всасывание

 

     С asing \ Cementing

Casing

It is generally not possible to drill a well through all of the formations from surface to the target depth in one hole section. The well is therefore drilled in sections, with each section of the well being sealed of by lining the inside of the borehole with steel pipes, known as casing and filling the annular space between this casing string and the borehole with cement, before drilling the subsequent hole section. This casing string is made up of joints of pipe (approximately 40ft in length) with threaded connections. Depending on the conditions encountered, 3 or 4 casing strings may be required to reach the target depth. The cost of the casing can therefore constitute 20-30% of the total cost of the well.

There are many reasons for casing off formations:

• prevent unstable formations from caving in;
• protect weal formations from the high mud weights that may be required in subsequent hole sections;
• isolate zones with abnormally high pore pressure from zones which may be normally pressured;
• seal off lost circulation zones;
• allow selective access for production \ injection \ control;
• provide structural support for the wellhead and BOPs.

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