Three important ways to complete the well

The completion of the well, as the name suggests, that is, the completion of the well, is the last step
before the production of the oil and gas well.
After the oil reservoir is drilled, the connection mode between the oil well and the oil and gas layer is closely related
to the direct test results of the oil, gas and water layer under the well and the development and exploitation of the oil and gas field in the future.
The well completion method of oil and gas mainly refers to the connection mode between the oil and gas layer and the well bottom, the well bottom structure and the completion process
.
Depending on the nature of the formation, different approaches to completion can be taken
.

The purpose of completion: (1) to effectively connect the oil and gas layer with the bottom of the well and minimize the resistance of oil and gas flow; (2) Properly seal and trap oil, gas and water layers to prevent mutual interference between each layer; (3) Overcome the impact of well wall collapse and oil layer sand production to ensure that oil and gas wells? Long-term stable production; (4) It can provide convenience for future underground workover operations and production increase measures (fracturing, acidification); (5) The process is simple, the completion speed is fast, and the cost is low
.

According to the connection mode between the oil well and the oil and gas layer, there are naked-eye completion, perforated completion, liner completion and gravel filling completion
.

1.
Naked eye completion

This method is drilled to the top of the oil layer, the lower oil reservoir casing, cement injection, and then drilled with a smaller diameter drill to open the oil layer, the biggest advantage of this completion method is that the oil layer is completely exposed, without any obstruction directly with the bottom of the well, so the oil layer not only has the largest infiltration area, but also the flow line is straight, and the resistance of oil and gas into the well is minimal
.

The disadvantage is that the bottom of the well is easy to collapse, it is not easy to prevent the oil layer from sand out, it is not easy to carry out layering operations, and the oil, gas and water layers are easy to interfere with
each other.
Therefore, the naked-eye completion method is used in a small range and can only be applied to a single oil and gas layer with strong and stable rock formations, and no oil, gas and water interlayers, and some multi-oil wells with the same properties of oil and gas layers, and at present, this method has rarely been used
.

2.
Perforation and completion

This method is currently the most widely used completion method
at home and abroad.
It is to drill the entire oil reservoir first, lower the oil casing to the bottom of the well, inject cement reinforcement, and then the lower incision gun to the oil layer part of the hole, through the casing and cement ring, open the channel
for the oil and gas to flow into the well.

The advantages of this completion method are: (1) can effectively seal and support loose and easy to collapse production layer; (2) It can separate oil and gas layers with different pressures and different characteristics, which is convenient for stratified testing, stratified mining and stratified production increase and other industries; (3) It can be determined according to the actual data of the production layer obtained by drilling center, electrical measurement and formation test, etc.
, whether to enter the oil reservoir casing, which can reduce or eliminate the blindness of the lower oil reservoir casing due to no oil and gas; (4) Pipelineless completion and multi-pipeline completion can be carried out; (5) In addition to naked-eye completion, it is more economical
than various other completion methods.

The disadvantage is that the damage of the washing fluid and cement in the production layer during the drilling and cementing process is more serious; Due to the limited number and depth of perforations, the communication area between the oil and gas layer and the bottom of the well is small, and the streamline curved perforation hole is concentrated, resulting in a large resistance of oil and gas flowing into the well, and it is not easy to prevent the formation from sand
out.

3.
Liner completion

When the oil layer is composed of loose sandstone with poor cementing, if it is completed with naked eyes, the oil layer is easy to collapse, and the bottom of the well is blocked by sand, so that the oil and gas flow leaching area is reduced
.
To do this, a pre-drilled bore is inserted under the naked-eye oil and gas layer, and the liner is hung on the oil reservoir by the liner suspension at the top of the liner, and the annular space
between the sleeve and the liner is sealed.
Oil and gas flow into the well through the holes in the liner, and this completion method is called the liner completion
.

Because the liner is the use of the sand layer in the oil layer to naturally form an arch to prevent sand, it is not easy to control manually
.
It is not possible to seal the oil, gas and water layers in naked-eye wells
.

4.
Gravel filling and completion

The gravel filling completion method is to artificially fill a certain size of gravel between the liner and the well wall, so that it plays the role
of sand prevention and protection of the production layer.
There are two commonly used gravel filling methods: naked-eye inner gravel filling and casing inner gravel filling
.
The former is to first lower the liner into the well, and then use the washing fluid to send the gravel to the annular space between the liner and the well wall; The latter is the filling of gravel in prefabricated gravel liners on the ground level and then down into the
well.

The advantage of gravel filling and completion is that the seepage area of oil and gas flow is large, the resistance is small, and at the same time, it can prevent the collapse of the oil layer, sand and plug the well, so the oil well has a long
life.
However, it is more complex in the completion process, the application requires that the oil reservoir conditions are relatively simple, if the conditions are complex, such as the oil layer contains a water layer, the oil layer is composed of several layers with different pressure and permeability, it is not suitable for selection, so as to avoid the future oil production when it is difficult to selective, fracturing, acidification, partial pressure mining, layered water injection and other measures
.