The horizontal well completion with stinger is usually used to control the bottom water cone. Although the pressure profile and the inflow profile along the horizontal wellbore can be divided into two parts by the stinger, these profiles have not really flattened. In order to flatten the pressure distribution and inflow distribution further, it proposes a new technology. This new horizontal well has multiple artificial bottom holes (MABH) along the wellbore and it has application potential. In order to verify the effectiveness of MABH technology, a model of horizontal well completion with MABH was established, and the production performance of different water cone control technologies was analyzed: conventional horizontal well, stinger completion horizontal well, and MABH completion horizontal well. The results show that the MABH technology has more advantages than the stinger technology. The uniformity of pressure distribution of the 6-MABH horizontal well is 55% higher than that of the horizontal well with string technology, and the uniformity of inflow distribution is increased by 65.25%. At the same time, although the operation of MABH technology is very simple, it should follow a rule of MABH installation: the position of the first MABH should be set at 242.5 m from the heel hole of the horizontal wellbore, and the other interval is 92.4 m.

The water cone is formed due to the pressure loss from the toe to the heel of the horizontal well [

In the early 1990s, Norwegian Hydropower engineers first proposed the concept of an inflow control device (ICD) and developed a tortuous flow control device to balance the influx of various parts along the horizontal well. Subsequently, the oil service company developed pipeline channel ICD, orifice plate ICD, automatic mixing ICD, and nozzle ICD [

On the other hand, technology of horizontal well completion with stinger was proposed [

In this paper, a new method is proposed to further flatten the pressure profile and inflow profile along the horizontal wellbore. This method is horizontal well completion with multiple artificial bottom holes (MABH). At the same time, the pressure profile and the inflow profile along the new horizontal wellbore have been theoretically studied.

In this article, we set up some independent annulus tubes through MABH to connect the base pipe (see Figure _{1} ≈ _{2} ≈ _{3}) is much better than the pressure drop difference between the reservoir and the conventional wellbore (_{1} < _{2} < _{3}). Then compare the new inflow profile (_{11} ≈ _{22} ≈ _{33}) with the traditional inflow profile (_{11} > _{22} > _{33}). Therefore, the heel-toe effect will be weakened.

Technology of horizontal well completion with MABH.

In order to explore the use of MABH technology to reduce the efficiency of the heel-toe effect, relevant theoretical calculations were carried out. The detailed calculation method is as follows.

Wellbore flow model: divide the horizontal wellbore into

Flow analysis of the wellbore’s infinitesimal section.

According to the law of conservation of mass, the equation can be expressed as follows:^{3}; ^{2};

When

Then, according to the principle of momentum, the equation can be expressed as follows:^{2};

Assuming that the flow rate is stable, and when ∆^{3}/s; ^{3}/s;

Similarly, pressure drop

The average frictional stress

According to the research results of Ouyang [

Value of

Flow state | Various mass flows | Constant mass flow |
---|---|---|

Laminar | ||

Turbulent |

The following equation gives the friction factor:

Here,

Reservoir inflow model: firstly, we make the following assumptions: ① The bottom water reservoir is homogeneous and infinite. ② There is a closed boundary at the reservoir top and a constant pressure boundary at the bottom. The distance between the upper and lower boundaries is

The above assumptions will affect the calculation results of the total output. However, the focus of this article is to study the performance of the inflow profile and the pressure profile of horizontal well. Therefore, these assumptions do not affect the results of this article.

First, the horizontal wellbore is divided into ^{3}/s; ^{2}; ^{2};

In addition, the percolation rate can be represented as follows [^{2};^{2};

When

Through the mirror image method (see Figure

Schematic of mirror image.

Here,

Furthermore, the potential of

Here,

Therefore, the reservoir flow in

The vector representation is given by

Here,

When

Therefore, the actual reservoir flow model is as follows:

In addition, there is oil-water flow interaction in production. Therefore, combining equations (^{3}; ^{3}; ^{3}/s; ^{3}/s; ^{3}/s; ^{3}/s; ^{2}; ^{2}; ^{3}/s; ^{3}/s.

The focus of this article is to study the performance of the inflow profile and pressure profile along the horizontal well. Therefore, single-phase flow or two-phase flow does not affect the results of this article and then the coupling solution takes single-phase flow as an example.

Step 1: if a set of bottom hole pressures along each

Step 2: divide the horizontal wellbore into

The centre pressure of the

The end pressure of the

where

Step 3: the

For segment _{21} can be calculated by equation (

From segment (_{1} + _{21}) to segment (_{1}), the centre pressure of the

From segment (_{1} + _{21}) to segment _{1}, the end pressure of the

where

The pressure of

A new set of bottom hole pressures can be obtained in section

_{1} + _{21}) to (

_{1} to segment (_{1}

For segment _{22} can be calculated by equation (

The centre pressure of the

The end pressure of the

where

The pressure of

A new set of bottom hole pressures can be obtained in section

The main flow

Step 4: repeat Step 2 and Step 3 to calculate corresponding pressure distribution controlled by the next annulus bottom hole.

Step 5: compare the pressure

Schematic of horizontal wellbore flow with MABH.

This article focuses on a new technology to improve the impact of horizontal wellbore pressure profile and production profile, so a single-phase flow model is used. Here, we have designed three schemes (Table

Schemes of different water cone controlling method.

Scheme | Method |
---|---|

1 | |

2 | |

3 | |

4 | |

5 | |

6 | |

7 |

Parameters related to XU-2 horizontal well.

Parameters | Value |
---|---|

_{e} (MPa) | 12 |

^{−3} ^{2}) | 500 |

_{h} (m) | 800 |

_{base} (mm) | 100 |

11 | |

^{3}) | 0.95 |

70 | |

30 | |

0.3 | |

_{ro} (dimensionless) | 0.82 |

_{stinger}/_{a} (mm) | 40/20 |

_{rw} (dimensionless) | 0.26 |

Figure

Pressure profile and inflow profile with different completions.

Figure ^{3}/d)/m. It can be seen from Scheme 2 that the difference can be reduced by using a stinger, but the inflow fluctuation range between the funnel point and the end of the wellbore is still very large, and the value of (2) is 0.0468 (m^{3}/d)/meter. It is worth noting that in Scheme 3, by using MABH, the value of (3) is only 0.01626 (m^{3}/d)/m. Compared with (3) and (2), the uniformity of the former is improved by 65.25% than the latter. Therefore, it can be concluded that MABH can further flatten the inflow profile.

Figure

Pressure profile and inflow profile with different installation conditions.

The annulus tube can be oval and can be extruded through a seamless steel tube. It is locked between the base pipe and the screen pipe by the support ring and crossover. Here, you can set a MABH on the cross ring and connect the MABH to the annulus and the base pipe (see Figures ^{2}, the cost of an annulus tube is about $ 610. This is the challenge of developing low-yield fields. But it is suitable for high-yield bottom water oil fields or gas fields.

Operation process of horizontal well completion with MABH.

The reason for the multidirectional flow in the base pipe can be obtained from the following equation:

The results show that, compared with the constant mass flow in the annulus tube, the various mass flows in the base pipe overcome the greater flow resistance. The reason is because there are perforated openings in the base pipe, but not in the annulus tube, so the additional

MABH technical mechanism.

Here are some suggestions and conclusions:

A new MABH completion method is established to solve the water coning problem. The main mechanism of MABH technology is to reduce the original pressure in the conventional horizontal wellbore by using MABH. The original streamline from the toe to the heel in a conventional horizontal wellbore is changed by multidirectional flow. Then, the pressure distribution along the base pipe can be flattened, and the inflow profile along the horizontal wellbore can be made uniform.

A coupling model of horizontal well with MABH and reservoir is proposed, which can be used to calculate the pressure loss and inflow difference along the horizontal well. Then, the dynamics of water control technologies are compared based on the output. The influence of the type of wellbore on the development effect is also discussed. Both methods can effectively control the pressure profile and the inflow profile, but the system with 6-MABH has significantly improved the pressure profile and the inflow profile than the system with stinger. The uniformity of the pressure distribution of the horizontal well using 6-MABH is 55% higher than that of the horizontal well using the stinger, and the uniformity of the inflow profile is increased by 65.25%.

Although the MABH structure is complex, the operation is simple and convenient. The cost of a MABH and an annulus tube with a length of 10 m and a cross section of 314 mm^{2} is only $ 610, which is a challenge for the development of low-yield oil fields. At the same time, the first MABH should be set at 242.5 m away from the heel hole of the horizontal wellbore, and the other interval is 92.4 m.

The .xlsx data used to support the findings of this study are included within the article and can be downloaded from

The authors declare no conflicts of interest.

This study was supported by Major Project of China National Offshore Oil Corporation 13th five-year plan (Grant no. CCL2018ZJFN0462).