Abstract

Deep and ultra deep oil and gas are mainly concentrated in basins such as Sichuan, Tarim, Junggar, and Bohai Bay. 

Deep and ultra deep well cementing faces a series of engineering problems such as ultra-high temperature, ultra-high pressure, large temperature difference in long sealing sections, and narrow gaps, posing serious challenges to cementing slurry.

In order to meet the development needs of different blocks and resource types, through continuous research and development, we have constructed  high-temperature and large temperature difference cement slurry system, Ultra high temperature cement slurry system, high strength and toughness cement slurry system, and high-performance high-density/ultra-high density cement slurry system, which solved a series of technical difficulties in complex deep and ultra deep well cementing, and has been applied on site with significant results, effectively supporting the safe and efficient exploration and development of deep and ultra deep oil and gas.

1.High-temperature and Large temperature difference Cement Slurry System

Deep and ultra deep well cementing faces challenges such as long sealing intervals, high temperatures, and large temperature differences. Under large temperature differences, the strength development of the top of the cement slurry column is slow or even super slow, which not only prolongs the drilling cycle and increases operating costs, but also affects the quality of cementing and even causes gas channeling.

Domestic and international research has been conducted on the technology of large temperature difference cement slurry for deep well long sealing sections. Schlumberger has developed a large temperature difference cementing slurry system based on AccuSET intelligent retarder, which is suitable for temperatures ranging from 49 to 121℃ and meets the conditions of cementing with a temperature difference of over 50℃ between the bottom and top of the cement slurry column. At low temperatures, the strength of the top surface of the cement slurry column develops rapidly and has been applied in two wells in the Middle East Φ177.8 mm casing cementing, and the cementing is in high-quality.

Our company formulated DOC-SMART, a multi-functional cement slurry system. The system is composed of DOC-G80L series fluid loss additives as main agents, retarders, defoamers and other additives as auxiliary agents. DOC-G80L series fluid loss additives is a kind of AMPS based copolymer, it controls fluid loss through absorption and aggregation, when used cooperatively with various kinds of retarders in the system, it can be used in a temperature range of 30 to 210℃ and apply to intermediate casing and tail pipe cementing. DOC-SMART cement slurry system contains three series: low temperature system, high temperature system and salt water system. 

More detailed information, you can search on our website www.dicoenergy.com in Cementing Additives.

2. Ultra high temperature Cement Slurry System

The high-performance ultra-high temperature cement slurry system is of great significance for the safety, quality, and long-term sealing of deep and ultra-deep well cementing operations. It is also one of the key technologies to ensure the smooth construction of 10000 meter deep wells.

Schlumberger prepared a high-performance cement slurry system through particle grading and ultrafine spherical Micromax weighting agent, with a maximum density of 2.90 g/cm³ and a usage temperature of 232 ℃. The system has high compressive strength, good rheological and stability properties.

Our company DICO formulated DOC-HIWI, a high density cement slurry system. The system is composed of different mesh iron ore powder with special grinding treatment as weighing materials, reinforcement materials and other additives as auxiliary materials. It has the characteristics of high density, good flowability, good settlement stability and high strength. The particle size gradation technology of high density cement slurry system reduces the porosity and improves the compactness of cement and the whole performance of the cement slurry cooperated with other additive materials.

This high density cement slurry system DOC-HIWI can be divided into three series according to the temperature and the well condition.

l DICO-HIWI LT General high density cement slurry system: suitable for general cementing, medium and low temperature high pressure well cementing.

l DICO-HIWI HT High temperature and high density cement slurry system: suitable for high temperature and high pressure well cementing.

l DICO-HIWI SL Salt water and high density cement slurry system: specific to salt-Gypsum Beds cementing.

More detailed information, you can search on our website www.dicoenergy.com in Cementing Additives.

3.High Strength and Toughness Cement Slurry System

During the drilling and production process of deep high-pressure gas wells, there is a significant change in temperature and pressure inside the wellbore, which can easily lead to the failure of cement ring sealing and abnormal pressure in the annulus. Tough cement technology is one of the key technologies to ensure the integrity of cement ring sealing, and has become a hot research and application topic at home and abroad.

Schlumberger developed the FlexStone flexible cement slurry system abroad, with a suitable temperature of 40-150 ℃, a density of 1.20-2.20 g/cm³, a cement stone elastic modulus as low as 1.38 GPa, and a linear expansion rate of up to 2%. It has been applied effectively in gas storage, fracturing stimulation wells, and heavy oil thermal recovery wells abroad.

Our company DICO formulated a Latex Polymer cement slurry system DOC-FlexCem. The system is composed of DOC-G81L and DOC-G80L as basic additives, latex DOC-GR5 and DOC-GR6 as core additives, retarding agent, dispersing agent and other additives as auxiliary additives. Latex polymer cement slurry system not only has the advantages of wide range of temperature, high temperature and salt resistance and performance stable of the multi-functional system, but also has the latex system’s functions of strong impact toughness in cement sheath. The system has better performance of reducing water loss, compactness, strong toughness, low permeability of the cement paste through the combined action of polymer's adsorption on cement particles and latex particles’ filling effect on cement gaps so as to improve cementing quality effectively and prolong the production life of oil well. 

The DOC-FlexCem system is mostly used in liner cementing required good cementing quality, oil layer cementing and other well cementing operation with special requirements.

More detailed information, you can search on our website www.dicoenergy.com in Cementing Additives.

4.High-performance High-density/ultra-high density Cement Slurry System

The exploration and development of oil and gas are gradually expanding towards deep and complex geological structural zones, and the probability of encountering abnormally high pressure formations is constantly increasing. The complex working conditions such as high annular pressure, wellbore instability, and high-pressure salt water layers in cementing are becoming increasingly prominent. High density cement slurry is a key technology for stabilizing the formation, preventing well kick, blowout, and ensuring the safety of cementing operations and the quality of annulus sealing.

Schlumberger developed DensCRETE cement through particle grading and the use of ultrafine spherical Micromax weighting agent, and prepared high-performance high-density cement slurry with good flowability, with a density of 2.00-2.90 g/cm³. It has been successfully applied in oil fields such as Mexico, Oman, and the South China Sea.

Our company DICO formulated a Resin cement slurry system DOC-ResinCem.This system contains resin as the core additive, its main function is to increase corrosion resistance of cement stone, and meanwhile decrease elasticity modulus of cement stone without sharply lowering the strength. Resin cement slurry possesses excellent anti-pollution capacity.General performance doesn’t change obviously when resin is added into the cement system, which makes it convenient to use.

This System has below Advantages—

l Decreasing permeability of cement stone and changing the hydrophily of surface of cement particles .

l Forming film on surface of cement particles and inhibiting gas flowing.

l Increasing adhesion of two interfaces of cement stone.

l Molecules designed for tolerating 30-200℃.

More detailed information, you can search on our website www.dicoenergy.com in Cementing Additives.