Heavy Oil Recovery Service

Through continuous scientific research and experimental exploration, COSL has developed the thermal recovery technology for heavy oil and a series of supporting technologies for surface equipment, and established the design methodology for offshore heavy oil huff-and-puff / displacement / SAGD production schemes. We have developed heavy oil production technologies and operational service capabilities, such as thermal huff and puff development, thermal displacement, thermal chemical compound efficiency enhancement, Integrated injection production, high-temperature plugging, electric heating, and enhanced cold recovery technology for heavy oil.

With the support of scientific research projects, we have undertaken 35 projects at or above the company level, including 3 national major special projects, 1 Tianjin Science and Technology Leading Enterprise project, and 5 scientific research projects of CNOOC Group. Adhere to independent innovation, continuously accelerate technological breakthroughs and accumulation, develop 11 sets of core software, develop 7 series of more than 20 thermal recovery tools, and develop 6 series of more than 20 chemical products for heavy oil recovery. Based on this, 6 CNOOC applicable processes and 11 key thermal recovery technologies have been developed, of which 9 technologies have reached the international advanced level.

Process Introduction

The multi-component thermal fluid huff-puff is a composite huff-puff recovery technology between steam (or hot water) and gas, and this technology adopts the burning spray mechanism used by the engine of space rocket, which takes the industrial diesel oil, crude oil or natural gas as the fuel, and then burns with the high-pressure air in the high-pressure combustion chamber of the rocket-power recovery equipment, and forms multi-component thermal fluid consisting of steam, CO2 and N2 for huff-puff recovery after adding injection water.

The synergistic effect of steam, gas or chemical agents, etc., is made full used for common offshore heavy oil, and it indicates that the productive results can up to 1.5 times of the conventional steam recovery through physical simulation and numeric simulation, and can up to more than 3 times of the conventional cold recovery capacity by applying multi-component thermal fluid huff-puff technology for offshore heavy oil.

The thermal-gas-chemical ' plug removal ' and ' synergistic ' effects of multi-component thermal fluids can dissolve organic precipitates such as wax, resin, and asphaltene, thereby relieving the shrinkage of the tubing due to the accumulation of organic precipitates such as wax, and relieving the blockage under the pump and the organic blockage in the screen or near the wellbore. At the same time, the injected hot fluid can effectively reduce the viscosity of crude oil, improve fluidity, and supplement formation energy, thereby improving the production status of low-yield wells.

Technical Applicability

Viscosity of reservoir crude oil: 350*～10000mPa•s

Target reservoir thickness ≥6m

Porosity: ＞10%

Permeability: >200mD

Primary oil saturation: >50% of heavy oil reservoir

Supporting Systems, Software and Tools

Supporting systems: thermal recovery technology design, ground equipment technology of thermal recovery, multi-component thermal fluid corrosion protection technology, gas channeling prevention and control technology, demulsification prevention and efficiency improvement technology.

Software: Thermal parameter calculation software for offshore heavy oil thermal recovery wellbore, optimization design software for offshore heavy oil thermal recovery injection string, software for multi-component thermal fluid corrosion prediction, etc.

Chemical products: reservoir protection, corrosion protection, anti-emulsion and demulsification, plugging and channeling prevention, viscosity reduction and oil displacement, plugging removal and injection enhancement.

Tools: wellbore safety control tools, whole wellbore heat insulation tools, horizontal section uniform heat injection tools, thermal pollution prevention tools, thermal sand control tools.

Application

This technology has been implemented in an oilfield in Bohai Sea since 2008, including thermal recovery huff-puff of old wells, the primary, the secondary and the third round of thermal recovery huff-huff of new wells, and the daily oil production is increased to 600 ton/day from less than 200 ton/day before cold recovery, with the recovery rate of up to 0.75%. The thermal recovery production capacity is increased by 1~2 times compared with that of cold recovery so as to develop the oilfields economically and efficiently.

Case Study

Some well in the southern area of A Oilfield is injected with 2,933 cubic meter of heat from May 9 to May 23, 2012, put into operation on May 27, which blew for 67 days, and the daily peak oil production reached 101 cubic meter/day, with cumulative oil production from open flow of 4,690 cubic meter; the thermal recovery capacity was 2.3 times of that achieved by the cold recovery at initial stage.

Process Introduction

The technology is through continuous injection of high temperature medium (steam, hot water, hot fluid, etc.) into the injection well, continuously heating and displacing the formation of heavy oil eventually produced by the production well, to obtain sustained, higher production. The main mechanisms include viscosity reduction, steam distillation, thermal expansion, degassing, oil miscible flooding, dissolved gas flooding, emulsification flooding and so on.

Technical Applicability

Reservoir thickness ≥8m

Net total thickness ratio of oil layer≥0.4

Viscosity of crude oil＜10000mPa·s

Variation coefficient of permeability＜0.7

Primary oil saturation≥0.45

Permeability≥20%

Supporting Systems and Tools

High temperature resistant step-by-step plugging adjustment technology : it can realize the step-by-step plugging adjustment function of far-well profile control, far-end plugging adjustment and near-well channel sealing; high temperature resistant oil displacement efficiency technology plays a good auxiliary effect on thermal displacement.

Test technology: distributed optical fiber temperature measurement technology, coiled tubing optical fiber monitoring technology, microseismic four-dimensional image monitoring technology, etc., can realize temperature and pressure monitoring, steam injection, production profile test, water detection, fracturing crack monitoring and other functions, for safe, efficient and economic development of offshore oil and gas fields to provide guidance and basis.

Long-term wellbore tools : high temperature annular safety packer, high temperature downhole safety valve, with through the thermal packer and other tools to ensure long-term thermal recovery displacement wells under high and low temperature alternating wellbore safety control, wellbore insulation.

Application

Steam flooding process and hot water flooding process have been implemented in Bohai Oilfield respectively since 2020, and are currently ongoing.

Process introduction

Thermal-chemical compound huff and putt technology enhancement function can be explained by two parts. Firstly, water on the surface, usually including water source well, produced water, seawater or other sources, is heated to the temperature of below 200℃ and injected into the reservoir to elevate formation temperature, reduce crude oil viscosity and increase heavy oil fluidity. Secondly, chemicals are applied to optimize the physical and chemical properties of formation and the fluids in it according to their special interface characteristics to improve huff and puff performance further. The technology meets the demands of thermal recovery production enhancement of cold production completion wells.

Technical applicability

Cold completion wells

Organic deposits, bad flow behavior or edge and bottom water breakthrough

Layer thickness ≥8m

Ground oil viscosity＜10000mPa·s

Original oil saturation ≥0.45

Supporting products

Chemicals commonly used involve oil-based multi-functional viscosity reduction and block removal agent, low-medium temperature high efficiency anti-emulsion synergist agent, multi-effect foaming agent, polymer gel agent and so on. With the utilization of these chemical agents, the oil production can be effectively increased for the wells of low production, low effectiveness and cold production completion.

Application

Thermal-chemical huff and puff technology has been mainly applied in Bohai oilfield. The accumulated injection amount of N2 has reached 1200000 cubic meter, water of 200000 cubic meter, with an accumulated oil production of 13400 cubic meter.

Case Study

Well B and C have encountered the development problems of “TWO HIGH and ONE LOW”, which are specifically referred to high viscosity(of 4032mPa·s), high water cut(of 75~90%) and low degree of extraction(of 0.2~0.7%). On the basis of such problems, three rounds of thermal-chemical compound huff and puff have been carried out for each well separately with extinguished performances of production fluids amount increase, water cut decrease from 90% before to less than 30% after, peak oil production of 5 times elevation and most accumulated oil increase of more than 4000 cubic meter for one single well.

Process Introduction

The reservoir electric heating technology uses the "Joule heating effect" of three-phase AC power to heat the formation crude oil. This technology transmits electrical energy to the wellbore through power cables and heating cables, and solves the problems of poor fluidity and difficult pumping of formation heavy oil through "centralized heating by downhole electric heaters" according to the actual needs of the oil well; At the same time, relying on supporting construction equipment, single well long-term reservoir electric heating and multi well intermittent reservoir electric heating can be carried out according to the production status of the oil well.

This technology has the advantages of short operation time, small equipment footprint, fast effectiveness, and long validity period, and has good application prospects in offshore oil fields.

Technical Indicators

Heating power: 100-200KW (heating line power 1-2KW/m)

Heating cable service life: ≥ 2years

Depth of descent: ≤ 3500m

Heating cable temperature resistance: ≤ 600℃

Power cable temperature resistance: ≤ 230℃

Technical Applicability

Extraction of heavy oil with high viscosity, high solidification point, and high wax content.

Application

At present, the reservoir electric heating technology has completed extensive testing in Bohai Oilfield and achieved good results.

Case Study

S well (heavy oil well)

After using reservoir electric heating measures, the wellhead temperature increased from 49℃ to 58℃, and the pump suction inlet temperature increased from 60℃ to 74℃. Currently, the well produces 131 cubic meter of liquid per day, 82 cubic meter of oil per day, and 37.4% water content. After the measures, the water content decreased by 5% and the daily oil production increased by 5 cubic meter, achieving the effect of controlling water and increasing oil production.

C well (High liquid production and high water content thick oil well)

After using reservoir electric heating measures, the wellhead temperature of the well increased from 65℃ to 75℃, and the pump suction inlet temperature increased from 72℃ to 78℃. Currently, the well produces 426 cubic meter of liquid per day, 67 cubic meter of oil per day, and 84% water content, effectively improving the flow state of crude oil in the formation and enhancing production efficiency.

Process Introduction

The wellbore electric heating technology heats the wellbore crude oil through the "skin effect" of single-phase AC power. This technology transmits electrical energy to the wellbore through steel armored cables, and solves the problem of difficult lifting on the pump through the "steel armored cable heating along the way" method according to the actual needs of the oil well; At the same time, relying on the auxiliary construction equipment, carry out electric heating for plugging removal without halt for a short period and long-term wellbore heating by electricity can be carried out according to the production status of the oil well.

This technology has the advantages of low cost, short operation time, small equipment footprint, and fast results, and has good application prospects in offshore oil fields.

Technical Indicators

Heating power: 50-200KW (single heating cable)

Service life of steel armored cable: ≥ 2years

Depth of penetration: ≤ 4000m

Cable temperature resistance: ≤ 250℃

Technical Applicability

Extraction of heavy oil with high viscosity, high solidification point, and high wax content.

Application

Since the 1990s, wellbore electric heating technology has been widely applied in various oil fields in China, achieving good economic results.

Case Study

D Well (Mechanical recovery well with difficulty in pumping)

After this well adopts electric heater, the daily fluid output reaches 19.7 cubic meter, water content of 67%, and daily oil production of 6.50 cubic meter. After heating the wellbore, as the temperature rise changes the oil-water mobility ratio at the immediate vicinity of wellbore, resulting in a decrease in water content and an increase in oil production, thus attaining the target of controlling the water-cut and improving the production.

E Well (Flowing well with high freezing point and high paraffin content)

After this well adopts electric heater, the daily fluid production reaches 11.4 cubic meter and daily oil production of 9.2 cubic meter, preventing the crude oil from paraffin precipitation, and the oil well could maintain normal production steadily. This well maintains flowing continuously for 4 months and then changes to mechanical recovery.

Heavy Oil Recovery Service

Process Introduction

Technical Applicability

Supporting Systems, Software and Tools

Application

Case Study

Process Introduction

Technical Applicability

Supporting Systems and Tools

Application

Process introduction

Technical applicability

Supporting products

Application

Case Study

Process Introduction

Technical Applicability

Supporting products

Application

Process Introduction

Technical Indicators

Technical Applicability

Application

Case Study

Process Introduction

Technical Indicators

Technical Applicability

Application

Case Study

Process Introduction

Technical Applicability

Technical Indicators

Application

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