Three-year treatment of Tahe 4th District in Northwest Oilfield to triple daily crude oil production

In the first 7 months of this year, in the first 7 months of this year, the natural decline rate of Tahe 4 in the Northwest Oilfield was estimated to be 5.
3%, the comprehensive decline rate was -15%, and the daily oil production remained stable at 620 tons
.

This shows that 7 months after the completion of the special comprehensive treatment, the block continues to show a good development trend

The Tahe 4th District has a mineral rights area of ​​56.
7 square kilometers and a proven geological reserve of 63.
45 million tons, which is a carbonate reservoir
.

The block was put into development in 1997, and it was in an "aging" state 10 years ago

At the beginning of 2018, Northwest Oilfield No.
1 Oil Production Plant and Exploration and Development Research Institute jointly launched the special comprehensive treatment of Tahe 4 districts.
Four key technologies were formed after 3 years of research.
After application, the natural decline rate of blocks decreased from 21.
8% to -4.
8%, which is a comprehensive decline.
The rate dropped from 21.
2% to -18.
66%.
The maximum daily output of crude oil reached 695 tons, the cumulative increase in oil was 167,600 tons, and the break-even oil price fell by 9 US dollars per barrel
.

　　The development well pattern basically failed before treatment, and 16.
27 million tons of reserves in the middle and deep parts were out of control

　　Three years ago, Wang Jiale, director of the Development Research Institute of the First Oil Production Plant, was very anxious about the development status of Tahe Four District: "The conventional water and gas injection methods have been exhausted, and the daily output of the block is still hovering at 220 tons
.

"

　　At that time, the production rate of Tahe Four District was 12.
7%, the oil production rate was only 0.
17%, and the comprehensive water cut was as high as 73%
.

　　"15 years of water flooding and 6 years of gas flooding.
If the measures are used too much, the effect is not satisfactory
.

Before the special treatment, we established a total of 126 water drive well groups with 10 failures; 12 gas drive well groups with 5 failures.

　　Northwest Oilfield decided to restructure the injection-production development well pattern in the four districts
.

Faced with complex reservoir conditions, the technicians of the First Oil Production Plant, the Petroleum Exploration and Development Research Institute, and the Petroleum Engineering Technology Research Institute sorted out four major problems that needed to be solved: difficult to describe the reservoir development system, difficult to understand the connection status, and reserves production.

　　"Each problem requires a lot of scientific research work
.

For example, if the description of the reservoir development system is not accurate enough, we have to solve the problem that the previous geophysical exploration means are single, the reservoir structure is not clearly described, and the theory and methods of the reservoir development law are not clear.

　　Rely on scientific and technological innovation to solve problems and tackle 4 key issues in 3 years

　　How to carry out special comprehensive treatment? Northwest Oilfield recognizes one principle: it must rely on scientific and technological innovation to solve problems
.

　　The technicians consulted almost all the technical data of carbonate reservoirs in the Tarim Basin, and based on the karst system research, carried out 4 detailed descriptions of karst systems, static and dynamic connected classification descriptions, fine classification and evaluation of reserves, and construction of three-dimensional well patterns.
Research on key topics
.

　　"In our research on the fine description of the karst system, we must first solve the problem of fine description of the reservoir, which is similar to laying the foundation for a new building
.

We must accurately locate and identify each cave, and even the specific location and location of each fracture or crack.

　　After more than 6 months of hard work, Zhang Ying and her colleagues have successively solved the difficult problems of reservoir development system description and fine understanding of connection status, and innovated and formed the fine description of the reservoir including the "three determination" technology of karst caves and the technology of fracture classification description.
Three key technologies are identified, which can finely identify the structure of the reservoir in the fourth district of Tahe, which provides a strong support for the description of the karst system
.

　　Zhang Ying introduced that based on three key technological breakthroughs, they innovated and formed the "five-step method" of fine description of the karst system, turning the complex and disorderly fractured-vuggy body into a regular karst system
.

At present, they divide the Tahe four districts horizontally into 3 main control areas, 6 main karst systems, 35 branch systems, and 8 dominant development areas for halls and caves, and vertically divided into 2 karst zones, forming an overall Macro karst pattern

　　In April 2018, technicians used the karst system fine description technology to re-understand the favorable oil and gas enrichment mode of the underground river in the fourth district of Tahe, re-understand the connection and separation at the sinkhole + hall cave, guide the construction of the well pattern, and deploy the new well TK495X Well, the daily output reached 40 tons, and the oil increased by 47,000 tons in 40 months
.

　　“We have also achieved important results in the research of three other key topics such as static and dynamic connectivity classification description.
Some of the results are domestic firsts and have good production and application effects
.

” Guo Zhongliang said, if they use three well pattern construction technologies, Six main karst systems were systematically designed, and 19 injection-production well groups were designed and constructed using methods such as new construction, adjustment, improvement, and optimization.
13 of them have been implemented, 11 of which have been effective, and a daily oil increase of 357 tons
.

　　The input-output ratio reaches 1:4.
8, and the experience is promoted in other old blocks

　　Up to now, the newly utilised reserves and newly added SEC reserves (according to the U.
S.
Securities and Exchange Commission criteria for oil and gas reserves) have increased by 5.
76 million tons and 1.
46 million tons respectively from three years ago
.
The seven main indicators, including natural decline rate, comprehensive decline rate, break-even oil price, reserve-production ratio, and reserve increase investment per ton of oil, were better than expected
.

　　"Not only has the output increased significantly, but the development benefits are even more impressive
.
At present, the cost of oil per ton in Tahe 4 District has been reduced by 377 yuan compared with before the treatment, the break-even oil price has been reduced by 9 US dollars per barrel, and the input-output ratio of special comprehensive treatment has reached 1:4.
8
.
"Said Liu Xiongwei, director of the No.
1 Oil Production Plant
.

　　Northwest Oilfield summarized and improved the comprehensive management experience of Tahe 4th District, and promoted it in other old blocks
.

　　In 2020, Northwest Oilfield will use the well pattern formed in the four districts to construct a series of technologies to comprehensively manage the Tahe second district
.
Relying on karst system depiction and other achievements, the technicians focused on the construction of gas drive well patterns in the northern part of the second district, and the improvement of water drive well patterns in the southern part, and finely constructed gas-water coordinated three-dimensional injection-production well patterns
.
So far, 9 well groups have been constructed in the second block, of which 6 have achieved obvious results.
The daily output of crude oil has risen from 200 tons before treatment to 295 tons, and the cumulative production has increased by 17,000 tons
.

　　At present, Northwest Oilfield is gradually promoting related technologies in Tahe 6, 7, and 8, which have the same reservoir characteristics
.

　　"The technological achievements we have achieved in the four districts are also of reference significance for the comprehensive management of old carbonate reservoirs of the same type at home and abroad
.
" Liu Xiongwei said
.
(Wang Fuquan and Zhao Chunguo)