The Technical Requirements for Dynamic Monitoring of Development Wells in Offshore Oil and Gas Fields formulated by China Offshore Oil Corporation stipulates the contents and requirements of dynamic monitoring data of oil, gas, water injection wells and observation wells in the oil and gas fields of the company. Its contents and requirements: single well productivity monitoring; Oil sampling requirements and water content monitoring of oil wells; Liquid property monitoring; Wellhead data acquisition requirements; Formation pressure monitoring; Monitoring of oil well liquid production profile; Monitoring requirements for water injection wells.
Second, oil and gas field monitoring technology
At present, oil wells artificially lifted at sea account for a large proportion. Due to the limitation of offshore production platform conditions, the artificial lifting methods are mainly electric submersible pump and gas lift oil production, and a few wells use screw pump, jet pump and booster pump. Therefore, the monitoring technology used is also different.
(A) Flowing well cable tubing logging monitoring technology
Huizhou 2 1- 1, Huizhou 26- 1 Oilfield and Xijiang 30-2 Oilfield adopt internationally advanced downhole operation monitoring system, and carry out production logging (PLT) through wireline operation technology with a series of instruments and tools to obtain data such as well temperature, zonal water cut, production and bottom hole pressure.
Conventional production logging can determine the liquid production position, fluid type and proportion, downhole temperature, downhole pressure and fluid flow rate of oil wells, monitor the reservoir consumption process, and find the water invasion position, gas invasion position and oil-water interface changes, which provides an important basis for oil well production allocation.
Through the systematic analysis of production logging data, we can grasp the reservoir changes and take corresponding measures to keep the oil well (or oilfield) in the best production state and solve the problems of high yield and enhanced oil recovery in the oilfield.
According to the production logging data of Xijiang 30-2 oilfield, it is found that the main reason that affects the oil production is that the water in the water layer flows back into the oil layer, so corresponding measures are taken to ensure the high-speed production of the oilfield.
At present, several models of three-phase inclined wells and horizontal wells have been established, and interpretation software has been compiled according to empirical formulas. It can qualitatively explain all downhole conditions and quantitatively explain more than 90% well conditions.
(B) ESP well monitoring technology
Through offshore oilfield exploitation practice, a set of monitoring technology series of ESP wells suitable for different reservoir characteristics, different production methods (separate production and combined production) and different string structures has been gradually formed: "Y" string testing technology; Testing technology of pressure measuring valve: testing technology of downhole pressure measuring devices (PSI and PHD); Capillary testing technology; Radio wave transmission test technology; Liquid level detection technology, etc.
1."y" string testing technology
Y-shaped string is a special string for oil production and testing of electric submersible pump wells, which is only suitable for oil wells with oil casings. As the name implies, the Y-shaped string refers to a Y-shaped joint installed at the upper end of the oil well production string, one side of which is hung with an electric submersible pump unit and the other side is hung with a test string that can reach the oil layer. There is a working cylinder on this side of the test string, and a plug is placed in the cylinder. During testing, the production plug is fished out by wire operation, and then the combined test tool string is lowered into the well together with the test plug, and the test plug is stuck in the working barrel, and the test tool string continues to be lowered to the predetermined test position for testing. This method can test the temperature, pressure and fluid production profile of oil wells at any position, and can be used for layered testing, single-layer production or multi-layer separate production wells, which solves the problem that ESP wells can be produced in layers without pumping oil and can be tested at any time. This technology is one of the main methods for testing electric pump wells in Bohai Bay.
2. Testing technology of pressure measuring valve
It is a mechanical pressure measuring device, which can't measure pressure by itself. It cannot be continuously monitored, but it can accurately measure the pressure and temperature at the pump outlet and inlet. It is suitable for single-layer or multi-layer commingled production wells with self-overflow ability. It has the characteristics of convenient operation in testing, easy handling when accidents occur in operation, low cost and so on. This technology has been applied in some ESP oil wells in Bohai Bay and Beibu Gulf in the west of South China Sea.
3. Testing technology of downhole pressure measuring devices (PSI and PHD)
It belongs to an electronic pressure measuring system and is a pressure measuring device lowered together with the completion string. It can continuously monitor and read the pressure and temperature at the pump hanger on the platform at any time, and the PSI test system can also test the thermal insulation performance of the underground unit system after shutdown. Suitable for single-layer production or multi-layer commingled production wells. This technology has been applied in some ESP oil wells in Bohai Bay and Beibu Gulf in the west of South China Sea.
4. Capillary steel pipe detection technology
The pressure is transmitted through the capillary steel pipe, which can work and monitor continuously. The downhole part of the device transmits the downhole pressure to the platform (ground) through capillary steel pipes filled with industrial nitrogen or helium, and the instruments on the platform are composed of pressure transmitter and data acquisition system. Its characteristic is that it can directly read downhole pressure and pressure recovery data at any time on the platform, and it has data storage function. This technology is generally used for long-term production monitoring, pressure recovery test, pressure drop test and interference well test of ESP wells. In addition, the capillary steel pipe pressure measuring device can be lowered into the oil layer to measure the pressure data of the oil layer section. Because there are no electrical components underground, the test equipment is generally durable, reusable and has high test accuracy. Capillary testing technology is suitable for single-layer production wells or multi-layer production wells. For example, Area J of Suizhong 36- 1 Oilfield is an unmanned platform, and the monitoring wells using this technology account for half of the total number of development wells on this platform. Field application shows that it is more durable than pressure measuring equipment such as PSI and PHD.
5. Radio wave transmission test technology
This is a new monitoring system for ESP wells developed in the middle and late 1990s. The downhole part is run along with the completion string, and a high-temperature and corrosion-resistant component with induction test functions of temperature, pressure, flow and density is installed at the lower part of the string, and the measured parameters are modulated into radio wave signals, which are transmitted to the ground (platform) in the form of radio waves. The ground (platform) is equipped with a monitor for signal reception and demodulation, which can demodulate and restore the received signal, and has the functions of display, storage and remote transmission. This technology has been used to monitor ESP wells in Huizhou 32-2 Oilfield and Huizhou 32-3 Oilfield, and achieved good results.
6. Liquid level testing technology
Liquid level testing technology is used to monitor the dynamic liquid level depth of electric submersible pump wells and analyze the liquid supply situation of oil wells. The test methods can be divided into echo level test (CJ-2 and WSC- 1 computer comprehensive test for air guns) and material balance level test. The dynamic liquid level of ESP well can be tested at any time without affecting production, and the supply situation can be analyzed. When using WSC- 1 computer comprehensive tester, its data is displayed by computer in the form of curve. This technology is simple to operate and widely used in submersible pump wells in Bohai Bay area. In Suizhong 36- 1 Oilfield, Chengbei Oilfield and other oilfields that mainly use ESP for oil production, the number of dynamic liquid level monitoring wells is not less than dozens every year.
(3) Gas well monitoring
The gas well monitoring system mainly adopts static pressure monitoring to observe the formation energy loss.
Yacheng/KOOC-0/3-/KOOC-0/gas field is located in the southern sea area of Hainan Island, and was put into production in June/KOOC-0/996+/KOOC-0/October/KOOC-0/,and the system pressure test was conducted twice a year on average. 1May, 1997, taking the opportunity of gas field equipment maintenance and transformation, the gas well was tested, pressure measured and pressure gradient measured five days after the whole gas reservoir was shut in. Obtaining the formation pressure of gas reservoir and estimating the utilization of gas reservoir reserves in the development zone has obtained extremely valuable information, which provides a reliable basis for subsequent stimulation measures and ensures the stable gas supply of this gas field.
Three. Dynamic analysis of oil and gas fields (1) Find out the reasons for low oil production and implement effective measures to increase production.
There are 6 development wells in Block J of 36- 1 Oilfield. It is predicted that at the initial stage of production, the average daily oil production of a single well is 94m3, the daily oil production of the whole region is about 1500m3, and the annual oil production is 50×1.04t. All oil wells are mined by electric submersible pumps, as shown in Figure 10-3 1.
Figure 10-3 1 Well Map of Developed Area of Suizhong 36-l Oilfield
1997 65438+February, the area was put into production, with an average daily oil production of 47m3 for a single well and 75 1m3 for the whole area, which was far lower than the plan forecast. Some oil wells also stopped pumping water because of insufficient liquid supply. Through dynamic analysis, the main reasons of low oil well production are found out. The research work starts from two aspects: one is to analyze and compare the static similarities and differences of data between Well 16 and adjacent areas A and B, and the other is to analyze the construction situation of drilling and completion operations to find out the possible influencing factors.
1. Static data analysis
Effective reservoir thickness (m): 56.8 in J area, 73.2 in A ⅰ area, 65.8 in A ⅱ area and 62.4 in B area.
Reservoir porosity (%): 32.6 in J area, 3 1.5 in A ⅰ area and 32.2 in A ⅱ area.
Average surface crude oil density (g/cm3): 0.962 in J area, 0.974 in AI area and 0.957 in A ⅱ area.
Several data that may affect the productivity of oil wells will not cause such a low production in J area.
2. Oil well correlation
Well A2, which is 350m away from Well J 13, is selected for comparison. See Table 10-26 for the results.
The comparison of adjacent wells proves that the low production in J area is not caused by reservoir factors.
Table 10-26j 13 and A2 comparison table
3. Drilling and completion operations
For the first time, shielding temporary plugging technology was applied in J area, and a strong protective layer was formed around the borehole wall. However, due to lack of experience, the particle size of the selected "shielding temporary plugging" bridge plugging is inappropriate and insufficient, which leads to some solid particles in the mud invading the near-wellbore zone during operation, blocking pores and seriously damaging the oil layer. In addition, Area A, which is adjacent to Area J, has been put into production for many years, which leads to the reduction of formation pressure in Area J, and it is easy to cause drilling and completion fluid to penetrate into deep oil layers and pollute oil layers during operation.
In view of the above analysis results, measures such as unblocking after acidification and replacing large displacement pump were taken.
The acidification effect in J area is obvious. See Suizhong 36- 1 Oilfield 10-27 Acidizing Effect Statistics and Comparison Diagram 10-32. The output of each well has been greatly improved, and the single well output of half of the wells exceeds that of 100m3d.. 1998, and only acidizing in Area J can increase crude oil by 22× 104t.
Table 10-27 36- 1 oilfield acidification effect statistics table
In addition, the fact that J area is acidized to increase production is related to AI area adjacent to this area. Although the output of AI area reached the production allocation requirements at the initial stage of production, the oil production intensity after acidification was still lower than that of J area (2.47m3/d.m). Therefore, 4 wells in Ai area were acidized in February, 1998, and the average daily crude oil production increased by 34m3.
(2) Study the adjustment measures and optimize the water injection scheme.
From 65438 to 0993, Chengbei oilfield has entered the stage of high water cut production, and the water cut of marginal oil wells has reached more than 90%, especially the sewage treatment of platform B is full. In order to improve the development effect and oil recovery, numerical simulation method is used to study the water plugging and shut-in of oil wells with high water cut at the edge. The conclusion of numerical simulation research is that shutting in wells or plugging high aquifers can increase oil and reduce water, thus reducing the sewage treatment capacity of the platform and the cost of oilfield development.
Figure 10-32 Comparison of oil production intensity before and after acidizing in Suizhong 36- 1 Oilfield Area J.
1994 Based on the ideal fitting result of oilfield production history (see attached figure 10-33), the point water injection in oilfield was comprehensively studied, the water injection scheme was optimized, and four water injection wells were designed. During the period of 1995, the structure adjustment of liquid production and water injection were carried out in the oilfield, and the development effect of the oilfield was obviously improved. The pressure of the oil well around the water injection well rises, the low pressure area of the oilfield disappears, and the gas channeling in the low pressure area is controlled. The gas channeling wells in the eastern gas cap area also resumed production, the production of oil wells around water injection wells increased, and the decline rate of oil production slowed down.
Figure 10-33 Fitting Curve of Simulated Production History of Chengbei Oilfield Reservoir
(three) the implementation of gas reservoir excavation, improve the degree of gas field reserves.
Yacheng 13- 1 gas field is located in the south of Hainan Island, with a gas field reserve of 907.9× 108m3, which is the largest gas field discovered offshore in China so far. The north block of the gas field is developed in the first phase, with a reserve of 602× 108m3. Six gas wells are designed, with a daily gas production of 98/kloc-0 /×104 ~ 990×104m3. The annual gas transmission is 29× 108m3 to Hong Kong and 5.2× 108m3 to Hainan Province.
The gas field was officially put into production on New Year's Day 1996. Its production dynamic characteristics are: stable output, stable gas-oil ratio and water production, and pressure drop law of gas field. 1May, 1997, when the gas field equipment was overhauled for 5 days, the static pressure of the gas production well was measured, and the pressure gradient of Well A5 was measured. Well A 1 and Well A3 were shut in, and the measured pressure values were inconsistent.
Based on the analysis of static pressure and dynamic data of Yacheng 13- 1 gas field, it is considered that the main gas-bearing sandstone in Yacheng 1~3m- 1 gas field is vertically divided into four gas-bearing groups, with a thin (1~3m) mudstone and siltstone interlayer between them. The solution is to fill holes for wells that do not completely penetrate the two gas reservoirs below.
From June 1998 and June 10 to June 1 1, hole patching operations were carried out in wells a 1, A4 and A5, and good results were achieved. Through hole filling, the wellbore pressure of gas well increases obviously, and the pressure drop of gas field slows down. Hole patching can not only make full use of the reserves in the lower pay zone, but also prolong the stable production period of Yacheng 13- 1 gas field.
(d) Understand the dynamic characteristics of oil fields and improve the development effect.
Weizhou 10-3 North Oilfield is located in the Beibu Gulf Basin of the South China Sea. It is a small carbonate buried hill bottom water reservoir with only 500× 104t of petroleum geological reserves. It was put into production in August 199 1, of which 5 oil wells have a daily oil production of 500 ~100 m3. Due to the premature water breakthrough in oil wells, the water content rises rapidly and the output drops rapidly. During the period of 1993, the dynamic characteristics of the oilfield were systematically analyzed. The contents include: water quantity, bottom water activity, driving type, the relationship between the height of limit water cone and oil layer thickness and perforation degree, and the relationship between oil recovery speed and production decline and water cut rising speed. The conclusion is that the oilfield has a large water volume (estimated water volume is 100 times of oil volume) and sufficient energy, which is driven by elastic water pressure. Making full use of natural energy can develop oil fields without water injection, but it should be noted that production with water cone is a common phenomenon. During the production process, the oil well production and production pressure difference shall not exceed the limit production and pressure difference, the production shall be controlled at 30.0% ~ 50% of the limit production, the oil recovery rate shall be 2%, and the perforation degree of oil layer shall be controlled at 10%.
During the period of 1993 ~ 1995, the oil recovery rate was too high, all above 3.0%, and the comprehensive water cut rose sharply from 5. 1% to 34.6%. By the end of 1997, the oilfield was abandoned because of its high water cut (about 80%) and low oil production, which made it difficult to maintain the operating cost of the platform. Through oilfield production practice, it is more clearly recognized that only by fully understanding the dynamic characteristics of reservoirs and conducting scientific management can the best development effect of such reservoirs be realized.