Well Cementing Technology

For decades, COSL has been committing on the cementing technology development and has accomplished solutions for high temperature and high pressure, deepwater, extend reach , ERD, horizontal, low porosity and permeability, ultra deep well, shallow gas, depleted reservoir protection, HTHP lost circulation proof, anti-corrosion, high pressure salts formation, anti-channeling and other complex downhole conditions. To deliver the competitively cementing service flow, COSL has established their core cementing engineering standard, processes, additives, cement slurry systems, cement sheath evaluation instrument and cementing equipment. In the last decades, COSL has accomplished and been identified their long term zonal isolation technologies by efficient solutions and customer recognition in field services.

With over thirty years HTHP well cementing experiences, COSL has developed series of HTHP well cementing technologies through researching and field practices. COSL Cementing delivers reliable zonal isolation within the entire life of well . Providing our customers with satisfied HTHP well cementing solutions.

HTHP oil and gas field exploration and production is more challenging in terms of zonal isolation and cementing slurry system design, as conventional drilling of oil and gas wells are declining.

The key technologies and innovation of high temperature and high pressure well cementing technologies include:

I. HTHP cement slurry system. Series of HTHP cementing additives have been developed which can withstand up to 500℉ of BHST and 23.37ppg of slurry density. It is very stable under high temperature with promising API fluid loss, short transition time, and low porosity of set cement.

III. Anti-channeling, corrosion resistance and stress resistance cement technology. A set cement stress-resilience and damage evaluation equipment was invented, along with additives and cement systems which prevent gas migration, corrosion and elastic enhancement were developed that solve the problems of gas migration and enable the long-term integrity of cement stone.

IV. Gas channeling analyzer and cement sheath contraction and expansion analyzer are patent pending

All above technical achievement has been successfully applied in more than 100 wells in South China Sea, Myanmar, Indonesia, Iraq and other regions. It has been recognized by customers for its problem solving and successful applications.

HTHP cement systems include:

-COCEM-HIWI high temperature and high density cement system

-COCEM-HT cement system

COCEM-Hiwi high temperature and high density cement system

High-pressure formation require heavyweight cements to restrain the formation pore pressure. COCEM-Hiwi cement system provides high-density cements up to 23.37ppg without vicious the slurry. It is ideal for high-pressure, high-temperature (HTHP) cementing application.

Features:

‒ Good rheology, easier slurry placement at small pressure window formations.

‒ Reduced risks associated with long WOC.

‒ Slurries allow being mixed on the fly.

‒ API fluid loss ＜ 50ml.

‒ Zero free fluid.

‒ High compressive strength and no strength retrogression.

‒ High solid content, good anti-gas migration performance.

‒ Excellent stability of slurries at high temperatures.

‒ Resistance to mud contamination.

‒ High-density slurry with low viscosity.

Applications:

‒ HPHT primary cementing

‒ Well control and whipstock plugs

EPS design stone (SEM)

Set Cement Sample

COCEM-HT cement system

COCEM-HT cement system is constructed by synthetic copolymer and others functional additives. Based on the Engineered-Particle size theory, optimized grain size of weighting agent provides good shield to gas or fluids invading from formation during the critical hydration period. When formation gas enters the cement slurry, the functional particles coalesces to form a coherent, low-permeability plastic film that reinforces the bridges between cement grains and blocks further migration in to the cement. The cement system also controls gas migration by improving cement bond to the casing and formation interfaces, and create a thin, low-permeability filtercake to reduce fluid loss.

Left Fig: Good Sedimentation property

Right Fig: Strength Development

Left Fig: sensitive property

Right Fig: 446℉ performance

While drilling, lost circulation seriously affects the efficiency and quality of well construction. Any lost circulation, either prior to cementing, or during cement placement and afterward, would directly impacts cement sheath. The consequences of lost circulation are as follow:

‒ Partly reduces annulus zonal isolation of cement sheath. Zonal isolation would be totally or partially failed due to cement not returns to the desired depth.

‒ Once los happened during cementing displacement, the displacement plan would be changed and the cementing fluids system would not suit for loss situation more, and the displacement efficiency could not be ensured Once the lost circulation happens, the mud displacement regime and program which is based on the Wall Shear Stress hypothesis would be undermined

‒ For the fracture-propagation formations, the intake-and-influx effect would affect the bonding of interfaces of cement and formation.

COSL provides the complete lost circulation prevention and curing technology in the whole cementing process from evaluation to field operation. Based on the constant research on mechanism and curing of lost circulation, the lost circulation prevention model and curing theory have been well developed and optimized. The new patented dynamic lost curing evaluation apparatus provides LCM and simulation of formation loss with the Geo-mechanics. Optimized LCM formulation with the assistance of evaluation instrument has been applied in field, and the performance is remarkable. COSL also has rich experiences on the ualtra-narrow pressure window and lost circulation cementing.

Self-owned intellectual property of Lost-Circulation

- COCEM-LET low density cement slurry system

- PC-B62SPC-B66S leakage-proof and plugging materials

- Dynamic lost curing analyzer

COCEM-LET Low density and high strength cement system

COCEM-LET cement system is a microsphere light-weight slurry system. The system is designed by Engineered-Particle Size distribution theory to maximize the solid content. By introducing pozzolanic and micro fine materials, a high compressive strength and low permeability cement can be achieved. The density of this system is 7.5-12.5ppg.

Features:

‒ Wide range of slurry weights for different fracture gradient formations and small pressure margin cementing.

‒ Different pressure rate of microspheres used for certain depth of casing cementing.

‒ Low filtration favors reservoir protection.

‒ Zero free fluid and excellent sediment control benefit anti-gas migration.

‒ Engineered-particle size distribution slurries bridge and plug the fracture to against lost circulation.

Application:

‒ Low fracture gradient formation.

‒ Long cement interval.

‒ Cementing for under-balanced drilling.

PC-B62SPC-B66S LCM

PC-B62S Lost-Circulation Material is a mixture of high hydrophilic and high dispersible fibers designed for bridging downhole fractures. It can be used in most cement slurry systems of COSL for low fracture gradient formation, long cementing interval and horizontal wells.

Features:

‒ As an inert material, it is compatible with most of cement additives.

‒ This fiber is high hydrophilic and dispersible, therefore it will not tangled in the cement slurries.

‒ It does not affect the API properties of cement slurry except viscosity. It improves compressive strength and ductility of set cement.

‒ It is insoluble in hydrocarbon, and does not soften within 500℉.

‒ Used with granular solid material, slurry can plug the 0.04inch crack under 1015 psi pressure.

‒ Relatively low dosage, 8.5 – 15 lbs per cubic meter slurry.

PC-B66S Lost-Circulation Additive is granular particle material with Engineered-Particle Size distribution design for maximize bridging efficiency. It can be used in most cement slurry systems of COSL when cementing low fracture gradient formation, long cementing interval and horizontal sections.

‒ It provides lost circulation control and a superior.

‒ Dry mix with cement or directly add to slurry mixing tank.

Dynamic lost circulation analyzer

Prior to cementing, the lost circulation is generally treated by LCM. Therefore the prevention and curing in cement placement is to against the micro facture that generated by hydraulic pressure. The fracture widens or narrows, extends or contracts by dynamic hydraulic pressure during fluids placement. A phenomenon of breathable formation has to be deal with. A dynamic lost circulation analyzer was invented to simulate this phenomenon and evaluate the ability of LCM slurry under various fracture dimensions and pressure programs. The device is composed of fracture simulator, nitrogen gas source with pressure regulator, lost-slurry collector and other accessories. The simulated fracture size can be adjusted between 0mm and 3mm. The maximum pressure of the experiment is 1015psi, and the temperature ranges from 68℉ to 194℉.

Parameters:

- Power supply: AC220V, power: 2000W.

- Gas source: nitrogen

- Maximum working temperature:392℉

- Maximum working pressure: 1015psi

- Back pressure:101.5psi

- Fracture size: 0mm-3mm adjustable.

- Cell capacity: 27.5in3.

- Ultrasonic measurable slurry collector size: 61in3

Dynamic lost curing evaluation equipment

For the unique environment and shallow hazards, the deepwater cementing is quite differences with shallow water and onshore cementing applications. It can be charactered as follow:

1. Low temperature environment, it is hard for cement to develop enough compressive strength for drilling the next section.

2. Small pressure windows. The safety drilling window is so small or even minus windows ever recorded, for the unconsolidated formation near the mudline, which would trigger fluid migration and lost circulation.

3. Shallow water flow. The over pressured sand and water may exist, which might invade the slurry during WOC and damage the bonding between cement and casing and even cause the failure of cementing job.

4. Gas hydrates. The gas hydrates will melt and liberate the hydrocarbon gas which leads to gas channeling, or even poses blowout and other serious consequences to the well.

Based on the abovementioned deepwater well cementing challenges, Oilfield Chemical of COSL has established series of deepwater and ultra-deepwater cementing technology. In the last 5 years, COSL has cemented one well with over 3380ft of water depth, and is capable to provide 9842ft deepwater well cementing services.

COCEM-LT low temperature cement system

The COCEM-LT low temperature cement system is the upgrade of COCEM-LoLET cement system. It presents better gas migration control property and rapid compressive strength development.

Comparison of Low Temperature Strength Development of different cement system

Strength Development

COCEM-DeepCEM low temperature and early strength cement slurry system

The PC-DeepCEM cement system is low temperature cement system. Its main components are PC-A92S and PC-A93L accelerators. The cement system can achieve sufficient compressive strength specified in API 10B-3. The slurry system can be used in deepwater surface casing cementing usually with low temperatures.it presents short wait-on-cement time which reduces rig costs.

COCEM-LoLET low hydration heat and low density cement system

COCEM-LoLET cement slurry system is applicable for deepwater where low temperature, narrow pressure window, and potential natural gas formation are commonly existing. It is composed by PC-DA34L and other functional additives and microsphere. PC-DA34L accelerates cement strength development with low hydration heat. The low density and high strength microsphere is added to reduce the slurry density. Under the strategy of the Engineered-Particle Size distribution theory, as a result, the stability and compressive strength of this cement system are much better than the conventional light weight slurry system and promises good performance in fields operations.

Features

‒ Low hydration heat;

‒ Good performance even at 35.6℉;

‒ Good solution to ultra-narrow pressure window.

Applications

‒ Deepwater surface casing;

‒ Low hydration heat required environment.

Hydration Heat of Different Cement Slurry Systems at Low Temperature

Shallow water flow cementing technology

The shallow water flow cementing technology is applicable for the potential or identified shallow water flow formation cementing in deepwater. The cement slurry system possess lost circulation control and anti-channeling properties,

Cement Slurry System Property

Set cement is subject to attacks by downhole corrosion fluids in the life of well. CO2/H2S corrosion inhibited cement is highly demanded for the oil and gas exploration and production.

Main related technologies:

‒ COCEM-Resin multi-functional cement system

‒ COCEM-Seal cement system

‒ SMART cement system

COCEM-Resin cement system

The COCEM-Resin cement system is resin added cement. The resin form films between cement particles which help reduce the permeability of set cement, therefore a strong resistance to sour fluids and gas tight cement is created. Resin material promotes the ductility of set cement which maintains the long term integrity of cement sheath. The cement wrapping resin film block the interaction between cement particle and oil-base mud which improves the resistance to oil-base mud contamination. The resin compound contains thermal functional group that improves high temperature stability of cement slurry to maximum 500℉, which is ideal for HTHP well cementing. Nevertheless, resin cement slurries also possess properties such like low filtration, low free fluid, better rheology and east to mix in the field. COCEM-Resin has been applied in many acid gas, shallow gas and HTHP cementing applications.

Applications

‒ Applicable for 40℉-428℉ well cementing operation;

‒ Applicable for the high temperature and high pressure, corrosive gas and shallow gas wells;

‒ Applicable for the offshore and onshore well cementing operations;

‒ The seawater can be used as base water for the cement slurry preparation;

‒ Available for the slat or/and gypsum environment cementing.

Features

‒ Strong capability of fluid loss control and zero free water;

‒ Excellent performance in high temperature application;

‒ Good strength development;

‒ Excellent anti-acidic corrosion and anti-gas migration ability;

‒ Simple composition and easy to use;

‒ Strong anti-contamination capability

‒ All-purpose cement system, applicable to various formations

Anti-corrosion Test

Anti-gas migration test

Electron microscope photo

COCEM-Seal cement system

The COCEM-Seal cement system is the system of synthetic polymer COCEM cement system which is thermal stable, salt tolerance and contamination resistance cement slurry reinforced by latex to achieve elastic and enhanced anti-gas migration performance..

Features:

‒ Zero free water;

‒ The fluid loss﹤50ml;

‒ High compressive strength;

‒ Excellent anti-gas-migration performance;

‒ Strong anti-contamination capability;

Applications:

‒ Applicable for the well cementing of high temperature and complex downhole-condition wells

Cement Slurry System Property

Cement bond

Gas well cementing, especially HTHP well, presents huge challenges for engineering and slurry designs. The objective is to achieve the integrity of zonal isolation within the life of well. Four technical approaches are considered effective to achieve the cement integrity behind the casing, they are, slurry design on transition phase, slurry resistance on gas invading, effective mud removal and lost circulation prevention and curing.

The fact of fluid migration is the consequence of under-balance of downhole hydraulic pressure between formation to cementing fluids. During the hydration of cement, the hydraulic static pressure is losing gradually within the cement column. If the annulus fluids’ hydraulic static pressure together with the slurry resistance force of gas invading is greater than the formation pressure will prevent the formation fluids or gas challenging and even migrate to the surface. The longer of the cement column is, the greater of hydraulic static pressure will lose. By reduce the slurry permeability, pore fluid viscosity, film bridging and

The Well Cementing Expert Team of COSL has been cultivated on the research and development on the downhole fluids channeling mechanism. Through decades of progressive researching and practice, comprehend HTHP Anti Gas-Migration theory, engineering strategies and cement slurry systems have been in last ten years. The reliable Anti Gas-Migration cementing solution, especially for HTHP wells, from COSL cementing expert and field team is at your services.

Core anti gas-migration cement slurry system includes:

‒ COCEM-Resin multi-functional cement slurry system

‒ COCEM-LifeStone self-healing cement slurry system

‒ SMART cement system

COCEM-Resin cement slurry system

The COCEM-Resin cement system is resin added cement. The resin form films between cement particles which help reduce the permeability of set cement, therefore a strong resistance to sour fluids and gas tight cement is created. Resin material promotes the ductility of set cement which maintains the long term integrity of cement sheath. The cement wrapping resin film block the contact between cement particle and oil-base mud which improves the resistance to oil-base mud contamination. The resin compound contains thermal functional group that improves high temperature stability of cement slurry to maximum 500℉, resulting in the applications of HTHP well cementing. Nevertheless, resin cement slurries also showing properties like low filtration, low free fluid, better rheology and east to mix in the field. COCEM-Resin has been applied in many sour gas, shallow gas and HTHP cementing applications.

Application:

‒ Applicable for 40℉-428℉well cementing;

‒ Applicable for the high temperature and high pressure, corrosive gas and shallow gas wells;

‒ Applicable for the offshore platform and onshore well cementing operations;

‒ The seawater can be used as base water for the cement slurry preparation;

‒ Available for the slat or/and gypsum environment cementing.

Features

‒ Strong capacity for control of fluid loss and zero free water;

‒ Excellent performance in high temperature environments;

‒ Good strength development;

‒ Excellent corrosion resistance and anti-gas migration capability

‒ Simple constitution and easy to use;

‒ Strong anti-contamination capacity

‒ Strong universality, can adapt to multiple formations

Anti-corrosion Test

Anti-gas migration test

Electron microscope photo

COCEM-LifeStone self-healing cement system

The COCEM-LifeStone cement system provides a durable cement sheath to help ensure well integrity and zonal isolation for the life of the well. The self-healing cement stone has low elasticity modulus, high Poisson's Ratio and better mechanical properties which help maintain the cement integrity under the downhole conditions The hydrocarbon response self-healing material will swell when in contact with oil or gas to resume the zonal isolation even small annuli or shatters have been created by downhole stresses and operations.

Features

‒ The cement slurry is stable without free water.

‒ Low elasticity modulus, high Poisson’s ratio.

‒ No special treatments when mixing and pumping in the field.

‒ Provides better and easier mixing than hydrophobic materials.

‒ Self-sealing properties
• Swells in the presence of liquid hydrocarbons or condensates.
• Shuts off liquid hydrocarbon flow through the cement matrix or micro-annulus.

‒ Improved ductility of cement, lower Young’s modulus, higher Poisson’s ratio
• Makes cement more resilient to stresses.
• Enhance durability of cement.
• Improves tensile to compressive strength ratio.

‒ Environmental Compliance.

Applications

‒ Cementing in fields with history of sustained casing pressure.

‒ High tectonic stress areas.

‒ Shallow gas formation.

‒ The packer-type liner tieback.

‒ Plug and abandonment.

The ERD well drilling normally penetrates complex formations with extra long open hole and narrow pressure window. When it comes to cementing, the precision ECD control, mud removal and casing centralization for extended cement column are critical and have to be addressed.

COSL with its rich experiences for both onshore and offshore ERD cementing experiences in association with ERD casing running, wellbore cleaning, casing centralization, accurate fluids placement, ERD customized cement slurry system, ECD and related simulation software, has been successfully accomplished multiple ERD well cementing in which contains complex downhole conditions, for instance, fault formation in South and East China Sea.

Well Name	Displacement (m)	Measured Depth (m)	Vertical Depth (m)	Horizontal-Vertical Ratio	Maximum Well Deflection (°)	Number of Fault
Panyu10-5-A1H	6688.32	7654.00	2416.02	2.77	89.67	3
Panyu10-8-A1	4276.01	6341.5	2537.42	1.69	82.40	2
Panyu10-8-A3	4662.43	5551.58	1916.97	2.43	80.50	1

Well Cementing Technology

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Self-owned intellectual property of Lost-Circulation

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Main related technologies:

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Core anti gas-migration cement slurry system includes:

Application:

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