Drilling a hole from the ground using mechanical equipment or manpower is called drilling. Usually such process refers to the exploration or development of oil, natural gas and other liquid and gaseous minerals and drilling wellbore and large-diameter water supply wells. Drilling is widely used in national economic construction and plays an important role.

From drilling to completion, a well needs to do the following three main tasks:

1. Break the bottom rock;

2. Move the broken rock (i.e. cuttings) to the surface;

3. Consolidate the well wall (referred to as cementing).

The completion of each well includes three stages: pre-drilling engineering, drilling engineering and well completion operations. Each project stage has a series of construction steps. The main procedures generally include: well location, road survey, foundation construction, derrick installation, moving house, equipment installation, primary drilling, secondary drilling, drilling, tripping, bit changing, drilling, completion, electrical surveying, putting casing, cementing operations, etc.

Completion refers to the process of connecting the bottom hole and the oil layer with a certain structure after the open hole is drilled to the designed depth. Completion is the last important link in drilling work, and it is also the beginning of oil production engineering, which is closely linked to future oil production, water injection, and the development of the entire oil and gas field.

The quality of oil well completion directly affects the production capacity and economic life of the oil well and even affects whether the entire oil field can be reasonably developed. In oil exploration, the completion of oil and gas wells includes drilling oil layers, selection of completion methods, cementing, perforating operations, etc.

When the production layer with low permeability is there or it is seriously polluted by mud, it is necessary to carry out stimulation measures such as acidizing treatment and hydraulic fracturing before the well can be completed. According to the geological characteristics of the production layer, different completion methods are used: perforation completion method, that is, drilling through the oil and gas layers, running into the oil layer casing, and perforating the production layer after cementing. This method is the most widely used. These include casing perforation completions and liner perforation completions.

Open hole completion is a completion method in which the casing is lowered to the top of the production layer for cementing and the production layer is exposed. This method is mostly used for carbonate rocks, hard sandstones and oil layers with relatively good cementation and relatively simple horizons. The advantage is that the exposed area of the production layer is large, and the resistance of oil and gas flow into the well is small, but it is not suitable for multi-oil layers with different properties and different pressures. And there are also Slotted liner completion method, and gravel pack completion method, etc.


Production wells traditionally refer to wells drilled for oil and natural gas extraction or converted to oil and gas production. However, production wells in a broad sense also include water injection wells, gas injection wells, and observation wells drilled for the development of oil and gas fields. A production well is a well field in the state of exploitation and production. It is used to directly produce underground oil and natural gas in the development of oil fields and gas fields, namely oil production wells (also divided into blowout wells, oil pumping wells and gas lift wells) and gas production wells.

According to the downhole pipe string integrity, annular fluid properties, annular pressure conditions, etc., and combined with the actual management needs of the site, the production gas wells are managed by classification.

According to the above classification principles, production wells are divided into two categories: (1) Normal production wells; (2) Special production wells.


At present, the casing head used in the field has an integral structure with its main body and flange, which is connected with the blowout preventer during drilling. After the drilling operation is completed, the oil well is converted to an oil production well, and the casing head must be equipped with an oil production wellhead.

Since the specification of the casing head flange is larger than the specification of the lower flange of the oil production wellhead, when installing the wellhead, an adapter flange struck must be installed between the wellhead and the casing head, which not only increases the cost, but also increases the installation height of the wellhead device. When the pumping unit is installed, the base should also be heightened, which brings difficulties to the installation of the pumping unit.

Therefore, Sanjack Company has developed a combined casing head that does not require an adapter flange when it is converted into an oil well after drilling.


The casing head structure consists of casing head main body (1), housing (2), casing hanger (3), locking block (5), sealing ring (6), drilling flange (7) bolts (8) etc.

Working principle, the upper part is the flange and the lower part is the housing. The flange is sleeved on the housing. It is locked by a locking block and sealed by a sealing ring. In order to prevent the flange and the housing from rotating relative to each other, the flange and the housing mating surface have multiple keys. The flange is designed in two specifications, one is the drilling flange and the other is the oil production flange. When drilling, the drilling flange is sleeved on the casing head housing.

After drilling, the operation is converted to an oil production wellhead, so the drilling flange is removed, and the oil production flange is used there. The oil production flange is directly connected to the oil production wellhead, which provides convenience for the installation of the pumping unit.


The combined casing head developed by Sanjack is especially suitable for drilling and oil production operations. It has a simple structure and easy installation. It not only saves the cost for wellhead installation due to conversion sub but also reduces the wellhead installation height and provides convenience for pumping unit installation.