Generally, the casing pipe is used in the cementing operation. Cementing has important meaning in engineering and economy. The quality problem will cause: Unable to the second or third mining. Can’t mine the second or third. make reserve calculation errors the fluid not need to mining may flow into the well Make production layer destruction。
Cementing technology content involves cementing scheme selection and determination, the slurry design and calculation, borehole preparation, the tool accessory usage, cementing equipment selection and accounting and cementing program design, etc. In order to get the reasonable design, the following effect factor should be considered.
Borehole--the depth of the well, the strata temperature gradient, hole diameter and the formation property etc. Drilling fluid—drilling fluid system is the most important factor to the cementing quality and cementing work success or failure. Clear understand the drilling fluid type and system, and theological properties in order to adjust the ahead fluid, cement slurry or drilling liquid property according to the need. Casing pipe—the size, pipe wall depth and the centering guide is needed or not. Casing tripping in treatment--running speed, midway circulation, and wash well time before cementing, displacement, etc. cement slurry—slurry design, cement amount, slurry prepared method, additive and cement slurry rheological properties ect. Slurry mixing equipment—cement truck number required, mixing type, displacing liquid and output volume.
Picture 1 cement truck
Cementing can be divided into the follow three processes: running casing, cementing
According to the different function and the casing depth, the casing pipe can be divided into the following several kinds.
Conduit: conduit generally is the first trapping in and the shortest casing string. The goal of downcomer is to prevent the light sand layer from polluting by the drilling fluid, and prevent shallow hole section being destroyed. The interval close to the ground is usually easy to break, because it is loose and not gravel layer.
The well close to the ground is usually easy to break, because it is loose gravel layer. Catheter usually also plays the role of improving circulating fluid height, and making it to return to the tank.
Surface casing: It is used to seal the relatively shallow loose formation and layer. In addition to protect borehole support technology casing and production casing, surface casing also can prevent drilling fluid, underground salt water, oil and gas pollute the surface water.
Intermediate casing: If it is need to drill deeper, usually the intermediate casing is needed to ensure the borehole safety. The role of the intermediate casing often is sealing the complex formation drilling fluid difficult to control with, and ensuring drilling successfully.
Production casing: running production casing is the main purpose of drilling a well. The production casing oil production tubing of one oil well. This casing isolated the oil reservoir and the other fluid, and also isolated the oil reservoir and other strata. This can form oil and gas channels, ensure long-term production, and meet the requirements of the mining and stimulation.
Usually the drilling and cementing is an alternating process. The follow is the simple introduction of common drill cementing process.
1 The first spud and surface casing cementing
After the drilling equipment being installed, making the first spud, drilling surface layer, making drill bit out, and running surface casing must be do next, and the preparing work before cementing should be done well immediately.
Firstly, open pump to cycle the drilling fluid. Because the space between well wall and the casing is small, so can use the high speed of drilling fluid to impact mud cake in the wall and meanwhile, adjust the performance of the drilling fluid, until circulation pump pressure is stability. In this period, cementing preparation work should be ready, mixed slurry should meet the design requirements, in order to ensure the cementing construction is success.
Before cement slurry is injected into the casing, certain amount ahead fluid should be pump into the casing. Commonly ahead liquid is spacer agent and washing liquid. Spacer is used to space the drilling liquid and cement slurry. And washing liquid can wash the mud in the well wall and enhance cementing quality.
After designed amount cement being inject, the stopper should be released, and then slurry displacement start. When the pump pressure increased suddenly, namely stopper arrived at the well bottom, pressure increased suddenly(say again touch pressure, stop the pump), waiting for solidification begin according to the recommended curing time. By test, if the entire cementing quality index is qualified, next working procedures can begin.
Picture 2 the first spud and surface casing cementing
2 The second spud and technology casing cementing
Secondary spud is the continued work after completing the first spud footage and surface casing cementing. Cementing process is similar with surface casing cementing process. Cementing process is similar with surface casing
Picture 3 the second spud and technology casing cementing
3 The third spud and production casing cementing
The third spud is the continued work of
completing the second spud footage and intermediate casing cementing. Production casing
cementing is similar with the surface casing cementing and intermediate casing
Picture 4 the third spud and production casing cementing