Since Sinopec began implementing the “going out†strategy in 2001, overseas oil and gas exploration and development business has developed rapidly. By the end of 2017, Sinopec has more than 40 overseas oil and gas exploration and development projects, distributed in more than 20 countries around the world, and annual oil and gas production. The equivalent of more than 4 000 × 104 t has become an important guarantee for the safety of China's oil and gas energy supply. In the process of developing overseas oil and gas exploration and development business, Sinopec has continuously adjusted its development strategy and overseas oil and gas resources structure according to the strategic needs of national oil and gas resources and the changes in the international oil and gas resources market. At present, Sinopec's overseas oil and gas resources mainly include: 1) deep/marine oil and gas, such as oil and gas blocks in Brazil, Angola, Nigeria, Cameroon, Iran, etc.; 2) low-grade oil and gas in old oil fields, such as Argentina, Kazakhstan, Colombia Oil and gas blocks in other countries; 3) Unconventional oil and gas, such as oil and gas blocks in the United States, Canada, Australia and other countries.
Drilling and completion engineering technology is the key to improving the efficiency of oil and gas development. The US “Shale Gas Revolution†once again proves that advances in drilling and completion engineering technology can significantly reduce oil and gas development costs and even change the international energy landscape. Take the Barnett shale gas field as an example. In 2004, the mining cost was US$0.177/m3, a single well. The drilling cycle lasted for 110 days. The technical innovations based on horizontal well drilling technology and staged fracturing technology led to a reduction in mining costs to $0.088~0.106/m3 in 2011 and a shortened drilling cycle to 18 days. Therefore, effectively supporting the drilling and completion engineering technology to support overseas oil and gas exploration and development is crucial to ensuring the realization of Sinopec's overseas oil and gas exploration targets. Lu Baoping analyzed the engineering and technical problems faced by Sinopec's overseas oil and gas exploration and development many years ago and proposed countermeasures. However, in recent years, Sinopec's overseas oil and gas resources have undergone major changes—deep/marine oil and gas resources exploration and development. The engineering geological environment is more complicated. The low-grade oil and gas potential and enhanced oil recovery in the old oilfields have become the new focus of attention, and the demand for low-cost development technologies for unconventional oil and gas has increased – all of which put new demands on drilling and completion engineering technology. At present, the international crude oil market continues to be sluggish, and it is even more urgent to achieve cost reduction and efficiency enhancement through drilling and completion engineering technology innovation.
To this end, the author summarizes the major progress of drilling and completion engineering technology in various overseas blocks of Sinopec in recent years, and analyzes the problems and challenges of drilling and completion engineering technology of overseas oil and gas fields under the new resource structure and low oil price market. Targeted development proposals were made to safeguard the implementation of Sinopec's overseas oil and gas strategy.
1 Technical status
As a large international oil company, Sinopec continues to pay attention to the development trend of international petroleum engineering technology in the development process, continuously improve the level of drilling and completion technology through technological innovation, and apply new speed-up tools to effectively improve the drilling speed and adapt to the complex formation and environment. Enhancement, the level of automation and intelligence of drilling and completion equipment is continuously improved, and the potential of using engineering technology to mine oil and gas reservoirs is obvious. The integration and application effect of drilling and completion engineering technology innovation in Yada oilfield in Iran shows that engineering technology advancement plays an important role in reducing oil and gas field development costs and improving development efficiency.
1.1 Drilling speed technology
The application of a range of drilling speed-up tools increases drilling speed and efficiency in complex formations. For example, the Canada Daylight project applied a hydraulic oscillator in the large displacement well drilling in the Warburg area. By generating periodic vibrations on the drilling tool to destroy the debris accumulation and reduce the sliding drilling friction, the top drive vibration mode was created to create the maximum level. The displacement of 2 973.00 m and the fastest ROP rate of 62.20 m / h; Brazil RSB project and Canada Daylight project in the hard formation or soft and hard staggered formation using PDC-cone composite drill bit, practice has proved that this drill gathers PDC bit and roller cone bit features high rock breaking efficiency, long life and high stability in hard formation, interlayer and high abrasive formation. Brazil BM-S-11 block φ660.4 mm The well drill adopts the composite drill bit, the average mechanical drilling speed is increased by 43.60%, the average footage is increased by 15.70%, and the unit footage of the target section is reduced by 27.33%. The Brazilian RSB project uses the “turbine drill + impregnated diamond drill bit†to drill the salt. In the abrasive siliceous carbonate formation, the turbo drill has the characteristics of full metal, high temperature resistance and high speed compared with the conventional screw drilling tool; compared with the conventional PDC drill bit, the impregnated diamond drill bit It has the characteristics of self-sharpness, long-term aggression and long life.
1.2 Complex formation and complex environment drilling technology
Drilling fluid density windows are narrow in many blocks overseas, so it is especially important to ensure drilling safety. Offshore projects in Nigeria, Cameroon and Angola generally apply pressure-controlled drilling technology to solve the problem of narrow-density window drilling; Iran Yada Oilfield applies pressure-controlled drilling technology to accurately control the bottom pressure of stress-sensitive formations, and to deal with the problem of drilling thick active asphalt layers, such as The S03 well is controlled by pressure-controlled drilling technology. The operation time of the asphalt layer is shortened to 25 days. Compared with the adjacent wells, the drilling fluid is saved 2 200 m3, and the drilling cost is reduced by 4 million US dollars. In order to improve the drilling speed of drilling, improve the quality of the wellbore and improve the drilling rate of the reservoir, the rotary guiding technology is generally applied to the directional wells and the large displacement wells in the offshore project. The Cameroon project applies φ120.7 to the φ152.4 mm wellbore. Mm small-size rotary guiding technology successfully drilled a horizontal section of 167.00 m long. The Apache project in Egypt applied casing drilling technology to reduce leakage and reduce the cost of building wells by $800,000 to $110,000. The Brazilian and Andean projects use expandable tailpipe hangers to solve the problem of directional deep well tailpipe sinking and packer seating. The SJ oil field in Argentina uses non-permeability anti-collapse drilling fluid to improve the shale inhibition capacity, the diameter expansion rate is reduced from 40% to 5%, the drilling cycle is shortened by 15%, and the single well drilling cost is reduced by 16%. Synthetic-based drilling fluid technology is commonly used in RSB offshore oil fields in Nigeria, Cameroon and Brazil. The drilling fluid has excellent inhibition, lubricity, safety, low temperature stability and environmental protection. The US MLJV project successfully implemented multi-lateral well drilling in the MISSI-LIME formation. The cost of drilling and completion of double-branched wells was reduced by 26% compared with the conventional method. The cost of drilling and completion of the three-branch wells was reduced by 44% compared with the conventional method, which made it impossible to have commercial exploitation value. The land unit has a development value.
1.3 Intelligent Drilling and Completion Technology
Drilling while drilling and logging while drilling technology are widely used in offshore operations. The Andean project uses active logging while drilling technology to ensure that the reservoir drilling rate is 100%. The Well Commander cycle bypass valve technology is used in conjunction with the pressure measurement while drilling, and the high concentration plugging and killing are pumped through the ball activation and shutdown. The liquid improves the cleanliness of the wellbore and prevents the occurrence of complicated underground conditions. Canada's Daylight project uses BlackBox while drilling memory storage device to record bit vibration and stick-slip information in real time, which optimizes drill bit optimization and drilling parameters. The project's “well factory†technology is mature, and 8 wells in a single well site are factory-based. The well depth is about 600.00 m, the drilling cycle is only 25 d, and the relocation cost is reduced by 40%. Intelligent completion technology realizes automatic management of reservoir real-time injection and production through distributed data acquisition, transmission, automatic analysis and diagnosis of oil well production status and remote automatic adjustment of downhole flow control valve. The Addax Nigeria project realized the simultaneous mining of three reservoirs through intelligent segmentation completion technology, which reduced the cost of drilling and completion operations and improved oil recovery. Through the remote real-time transmission technology, the NGEC project in Colombia realized the real-time monitoring of the drilling-oriented geosteering operation in Beijing-Bogot-Drilling site and improved the drilling rate of the oil layer.
1.4 Improve oil and gas production engineering technology
In response to the geological characteristics of overseas blocks, advanced petroleum engineering techniques have been applied to increase oil and gas production. The St. Lakes Energy Project in Colombia uses an optimized foam profile control process (optimizing the timing, method and process of injection), and the average single well production is increased by 150%; the tight sandstone oil and gas horizontal wells from Canada's Daylight project are introduced into the “well factory†technology to achieve a single Synchronous fracturing of 8 well clusters in the well site, the number of staged fracturing stages is up to 40, the output of single well is nearly doubled, the operating cost is reduced by 30% compared with the conventional fracturing of similar wells; the Cameroon project introduces concentric annulus In the filling system, the success rate of gravel filling is 100%, and the yield increase effect is obvious. The oil-based drilling fluid is used in the Zarze project in Algeria. The drilling fluid density is controlled at 0.84~0.95 kg/L, which realizes the reservoir near-equilibrium pressure drilling and reduces Reservoir pollution; low-injury fracturing fluid applied to SJ oil field in Argentina, the average output per well increased by 25% compared with conventional fracturing technology; Iran Yada oil field applied self-steering acidification technology to solve heterogeneous carbonate reservoir The problem of uniform acidification in long horizontal sections increased the yield per well by 5.5 times.
1.5 Technology Innovation Integrated Application Effect
Integrated application of technological innovation is an important way to reduce the overall development cost of oil and gas fields and improve development efficiency. Take the Iranian Yada oilfield as an example. The oilfield is the first large-scale integrated oilfield of 10 million tons designed, constructed and operated by Sinopec. Since the drilling construction began in 2010, the oilfield has been optimized and efficient through the well structure. The application of rock-breaking tools, optimization of drilling fluid system, and research on asphalt layer drilling technology, the construction period was shortened by 63.0%, the average non-production time was shortened by 31.7%, and the cumulative investment was USD 89.4 million.
2 Problems and challenges
The drilling and completion technology of Sinopec's overseas oil and gas fields has obvious effects on improving quality and efficiency, but there are still problems such as uneven development of technology between blocks and weak competitiveness of independent technologies. The continued downturn in the crude oil market, the increasingly stringent international investment environment, the complex engineering geological environment under the new resource structure and the urgent need for technological innovation have all challenged the drilling and completion technology of Sinopec's overseas oil and gas fields.
2.1 Problems
2.1.1 Unbalanced level of technological development among overseas blocks
Although the application of a series of advanced and efficient drilling and completion engineering technologies has produced huge cost reduction and efficiency enhancement effects, some overseas blocks still use conventional drilling and completion technologies. The main reasons are:
1) Some overseas blocks have good geological conditions, and the drilling and completion technology has little challenge. Conventional engineering technology can meet the drilling and development needs; or it is limited by the overall technical level of the resource country market. The introduction of advanced technology is difficult or costly, which is not conducive to oil and gas resources. Economic development.
2) The drilling and completion engineering technology of some overseas blocks is weak. After the acquisition, the scientific and detailed engineering technology adaptability evaluation has not been carried out. Instead, the engineering technology plan before the acquisition is used. The advanced and effective technology has not been applied, resulting in construction efficiency. Low and high investment costs.
3) The information sharing mechanism between overseas blocks is not mature, and successful experience cannot achieve rapid sharing, evaluation and transplantation, and it is unable to exert the advantages of integrated information resources. For example, Canada's Daylight project uses horizontal hydraulic drilling, hydro-steering drilling and one-drilling technology to drill horizontal wells with an average mechanical drilling rate of 15.0 m/h. It can be used for technical upgrading to achieve horizontal well drilling and efficiency improvement in other overseas oil and gas fields; Brazil RSB And the Daylight project in Canada uses PDC-cone compound drill to drill soft and hard staggered formations, which can be used as a reference for speeding up the drilling of KOA soft and hard staggered formations in Kazakhstan and prolonging the service life of drill bits. The real-time tracking technology of drilling information has been applied in major offshore blocks and projects in Canada and Andes, while the drilling informatization level in other blocks is relatively low, which is not conducive to data efficiency and efficiency management. Technologies such as the North American shale gas “well plant†and automated drilling rigs also have the potential to be applied to other conventional oil and gas fields to increase operational efficiency and reduce costs.
2.1.2 Sinopec's independent research and development technology is not competitive
Sinopec's overseas projects involve many countries and regions, and the level of technology application is uneven. Although these years focus on the promotion and application of independent R&D technology, it is still not competitive with international large-scale oil and gas technology service companies. Sinopec's independent research and development technologies currently used in overseas blocks are mainly conventional drilling and completion tools and chemical additives (such as PDC drill bits, screw drills, tail pipe hangers and casing accessories, drilling fluids and cement slurry additives). Value-added technology and integrated supporting technologies are less used. Geotechnical drilling, casing drilling, rotary steering drilling, offshore fine pressure control drilling and intelligent completion technologies are mainly in the hands of large international oil companies or technical service companies, such as Shell, Schlumberger, and Halliburton. As Sinopec's overseas exploration and development gradually enters the difficult areas of deep, deep water and unconventional resources, the requirements for the technical level of drilling and completion engineering are getting higher and higher, and the technical monopoly of international large oil and gas technology service companies leads to high service costs. It is not conducive to reducing operating costs.
2.2 Challenges
2.2.1 The international oil price fluctuates at a low level, and the pressure for cost reduction and efficiency is still relatively large.
Under the influence of rising crude oil production, oversupply, crude oil market bearish expectations and international geopolitics, international crude oil prices are unlikely to achieve a high rebound in the short term, according to the US Energy Information Administration's (EIA) forecast of July 2018. Brent crude oil prices will have a high probability of below US$80/barrel by 2020. At present, most scholars believe that oil prices will fluctuate for a long time, and the “winter†period of the oil and gas industry will not end in a short time. Under the low oil price situation, some drilling and completion engineering technologies will lead to excessively high crude oil development costs, even exceeding the economic exploitation limit. How the drilling and completion technology can adjust the management strategy to quickly reduce the engineering cost and increase the oil and gas production, which is urgently needed to be solved. problem.
2.2.2 Resource laws and regulations, contract terms are demanding
The contract model of international oil and gas resources cooperation projects is becoming increasingly demanding. Taking the repurchase contract as an example, the oil company needs to recover the cost within a short contract period. How to ensure that the overseas project achieves the maximum investment benefit in a short period of time is a problem that needs to be solved in the drilling and completion engineering technology. Safety production and environmental protection have become the most basic and important requirements for international oil and gas cooperation. For example, Russia's Sakhalin and other projects require “zero emissions†such as drilling fluid, cuttings and waste water; in order to protect drinking water resources from pollution, the United States Some states have successively banned the use of hydraulic fracturing technology to extract natural gas; Argentina has increasingly tightened the approval of well sites to protect forest resources.
2.2.3 Long drilling cycle and high cost in complex geological environment
1) Drilling pressure control of narrow density windows at sea is difficult. The pore pressure in the reservoirs in the offshore blocks is generally high and the overburden pressure generated by seawater is low, resulting in the shallow formation being easily broken. The narrow-density window problem is common in offshore blocks, and the deep-water block is more prominent. Drilling and spraying problems in the drilling process are serious, resulting in long non-production time, high risk of well control, long drilling cycle and high engineering cost. In the deep water block of Brazil PDA (water depth 2 600.00~3 000.00 m), the fractures and karst caves of the limestone strata are developed, the safety density window is narrow (0.02~0.05 kg/L), and the drilling fluid lost in the PDA-1 well during drilling is about 12 000. M3, single well non-production time of 841 h, drilling costs increased by 60 million US dollars. Overflow occurred during the static flow test of the Asangga-2 well φ165.1 mm section in the Addax OML137 block (water depth 65.00~496.00 m) off the coast of Nigeria. The well lost during the well killing, and the non-production time accounted for up to 32.0%.
2) Complex formations have long drilling cycles and high costs. Traditional drilling problems such as difficult operation in high temperature and high pressure environments, low drilling rate in hard formation/soft and hard staggered formations, lost circulation, and wellbore instability still exist in some overseas blocks. The average water depth of the Ngosso block in the Cameroon project is 2.00~3.00 m, the reservoir pore pressure equivalent density is 1.94~2.08 kg/L, and the bottom hole temperature is up to 196 °C. Overflow, loss, wellbore collapse, etc. occur in the AZOBE-1X well drilling process. In complex situations, the drilling cycle was 22.71 days longer than the design cycle, and drilling costs exceeded $20.5 million. The drilling depth of the KOA oilfield in Kazakhstan is 3 000.00~3 200.00 m, and the average drilling period is about 110 d. The strata are mostly gravel, salt, giant salt paste, plastic mudstone, shale and carbonate. Some of the formations have strong abrasiveness, resulting in low mechanical drilling speed, difficulty in well inclination control, frequent collapse and leakage, and non-production time ratio of 11.8%.
3) The high-strength, high-abrasive formation has a low rate of mechanical drilling. Some of the strength and abrasiveness of the formation are low in mechanical drilling speed, resulting in an increase in the operating cycle and the challenge of speeding up the drilling. Especially in the deep water block where the daily operating cost is high, the increase in operating time leads to a rapid increase in operating costs. The middle and lower parts of the subsalt reservoir of the RSB project in Brazil are hard silicified carbonate rocks with vermiculite and shale. The uniaxial compressive strength is 240 MPa. The actual drilling data of 3 wells in the PDA structure indicates that the average single drill bit is measured. At 45.00 m, the average ROP is only 1.29 m/h.
2.2.4 Special reservoir oil and gas resources are difficult to use
1) It is difficult to identify unconventional oil and gas reservoirs. Compared with conventional oil and gas, the lithological characteristics and accumulation conditions of unconventional oil and gas are more complicated. The strong heterogeneity and anisotropy of the reservoir lead to more multi-solution of geophysical response, and the identification of “dessert†is more difficult. For example, the main target layer of the US SDA project is the Mississippi layer, which is developed by horizontal well-stage fracturing. However, the water content in the initial stage of mining is more than 80%, the identification of reservoir “dessert†is inaccurate, and the distribution of oil and water is unclear. The development results are not ideal, and the reservoirs need to be carefully evaluated based on comprehensive geophysical techniques.
2) The efficiency of the oil wells in the old oilfields is large. Sinopec's overseas oil and gas production mainly comes from the development of middle and late oilfields. The phenomenon of “double high†(high recovery and high water cut) is prominent. The recoverable reserves of some oilfields are higher than 80% and the water content is higher than 80%. Compared with the domestic old oilfield development practice, the degree of refined management of overseas oilfields is relatively low, and there is generally no systematic and comprehensive treatment measures, and there is a greater potential for improving the efficiency through domestic technology transplantation. How to use engineering technology to achieve stable oil control and increase single well production has become an urgent problem to be solved.
3) Difficulties in the completion of well completion wells. The problem of liquidity protection such as sand production, deep water gas hydrate, asphalt and wax precipitation is widespread in overseas blocks, hindering the smooth flow of oil and gas pipelines and the realization of production targets. The formation of the FIOC block in Kazakhstan is loose and severely sanded, mainly using casing perforation completion (some wells are screened for completion), the sand control operation well has a short workover period (6~12 months), and the single well production is low ( 1~5 t/d), the development effect is poor; the sandstone reservoirs of the Moriche and Jazmin heavy oil fields in St. Lake Energy, Colombia are shallow (400.00~600.00 m), medium and high permeability, poor cementation, high viscosity of crude oil, and heat production by steam stimulation The sand is serious, the sand control period is short, the difficulty is large, the effect is poor, and even the slanting screen is blocked and deformed. The Brazilian RSB project uses a large amount of methanol injection to suppress the formation of natural gas hydrate during the production process, and still cannot prevent the formation of gas hydrate formation. Production of pipe string, natural gas hydrate blockage in the production process of PDA well 4 times, of which 2 times caused the gas well to stop production; Iranian Yada oilfield uses the Fahliyan reservoir as the target layer of the production well completion test when the asphaltenes in the crude oil are deposited and attached On the inner wall of the tubing, the tool entering the wire is blocked, and the five wells are difficult to remove the plug due to the precipitation of the asphalt in the tubing; the asphaltene of the MEN block in the SJ oil field in Argentina The CO2 content is high, the production pressure difference is large, and the production scale is severely scaled, causing the production pipe string to be stuck and corroded. The scaled well section is even as long as 200.00~300.00 m, using segmented acid cleaning and sleeve milling, and the single well operation cost. It is 80 to 1 million US dollars.
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