Salt-Tolerant Cement Systems to Mitigate Gelling Effect

Campos, Gilson; Simão, Cristina Aiex; Miranda, C.R.; Patil, Sandip P.; Deshpande, Abhimanyu; Patil, Rahul; Ravi, Kris

doi:10.2118/170477-ms

Cited by 7 publications

(3 citation statements)

References 7 publications

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“…The rationale for using salt saturated water is explained in a separate paper concerning cementing through salt zones (Campos et al 2014). The rationale for using salt saturated water is explained in a separate paper concerning cementing through salt zones (Campos et al 2014).…”

Section: Slurry Compositionsmentioning

confidence: 99%

An Experimental Study on Effects of Static CO2 on Cement under High-Pressure/High-Temperature Conditions

et al. 2015

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Downhole CO 2 in the presence of water forms carbonic acid, which reacts with cement. Some of the final products are water soluble and are leached out. This could cause loss of long term mechanical integrity of the cement sheath, among other issues. Hence, long term prediction of cement sheath carbonation is important to help ensure the cement system designed for CO 2 environments creates and maintains zonal isolation throughout the life of the well. This paper discusses a series of long term tests performed to better understand the effects of CO 2 on cement quantitatively. CO 2 downhole generally falls within two categories-dry CO 2 , which is a result of carbon capture and sequestration (CCS) activities, and wet CO 2 , which accounts for naturally formed CO 2 . Cement samples are tested under downhole conditions of high-pressure/high-temperature (HP/HT) in two different environments-supercritical CO 2 and carbonic acid, which represent the two different types of CO 2 present in the wellbore, respectively. Different types of cement blends have been used in the study to understand the effects of cement composition on corrosion caused by CO 2 .Cement samples were periodically withdrawn from the autoclaves to test for transient permeability, compressive strength, Brinell hardness, and chemical composition (X-ray diffraction [XRD], inductively coupled plasma [ICP] tests, pH indicator testing, and thermogravimetric analysis [TGA]). All of the samples were tested for a total of one year. It was observed that chemistry played a very important role in determining how resistant the cement is to attack from CO 2 .This study helped provide clear insight into a method that can be used for testing different cement blends for long-term integrity under varying corrosive environments. Knowing the performance of particular cement chemistry under downhole conditions provided considerable benefit in terms of understanding long term integrity of the cement sheath.

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Section: Slurry Compositionsmentioning

confidence: 99%

An Experimental Study on Effects of Static CO2 on Cement under High-Pressure/High-Temperature Conditions

et al. 2015

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“…Table 2 shows properties of these cement systems. The first system is the salt saturated slurry, the pumpability of which is not affected by the contamination of complex salts, such as Tachyhydrite (Campos et al 2014). The second system is fresh water based slurry used as the reference.…”

Section: Cement Systems Detailsmentioning

confidence: 99%

Design Procedure for Cementing Intercalated Salt Zones

Jandhyala

Ravi

Anjos

2015

Day 1 Tue, October 27, 2015

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Wells often require being drilled through and cemented across salt formations. In many parts of the world, salt sections consist of multiple salt types. These include Halite, Carnallite and Tachyhydrite. The last two salt types could move one hundred times faster than Halite and are chemically reactive. Typically, Carnallite and Tachyhydrite occur as streaks inserted between Halite. In these cases, cement sheath should withstand salt creep loading. Creep load is primarily compressive in cases of single salt types. For intercalated salts, varying creep rates can result in tensile loads, particularly at salt-salt junctions. Presalt exploration in offshore Brazil is an apt example displaying this behavior. In such a scenario, the cement sheath along a longitudinal well section should be analyzed for both tensile and compressive responses. It is well known that tensile strength of conventional cement systems is low, hence there is the need for detailed analysis and action to prevent damage to cement sheath.This work demonstrates cement design procedures by evaluating cement sheath mechanical integrity in intercalated salts. A typical presalt Brazilian well with different lengths of Tachyhydrite, Halite, and Anhydrite sections is used as an example in this work. A creep model for these salts is validated with data from triaxial creep testing. Responses of two cement systems, which are cured and tested, are compared. The analysis accounts for classical well loads during drilling and production etc., along with salt creep loading.This analysis shows that intercalated salts subject cement sheath to a series of tensile and compressive loads whose magnitude depends on the size and relative position of different salts. The salt-salt interface effects dominated the general tenet of increasing creep rate with increasing depth.This kind of detailed design procedure representing intercalated salt zones is the first of its kind known to the authors. Results from this analysis help fortify the importance of considering salt layering patterns during cement design for long term mechanical integrity. The design procedure discussed and presented in this study should help the industry design cement systems to withstand loads across single and intercalated salt zones and maintain well integrity.

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“…Hereafter, these slurries are referred to as NC-FW, NC-SS, RP-FW, and RP-SS. The rationale for using salt-saturated water is explained in a separate paper concerning cementing through salt zones (Campos et al 2014). The concept of using the same cement blend differentiated only by the mix water encouraged the authors to investigate salt-saturated mix water for the slurries (Aiex et al 2015), the concern being what would transpire if the salt saturated slurry were placed in the reservoir section containing CO 2 .…”

Section: Slurry Compositionsmentioning

confidence: 99%

Long-Term Study of Effects of CO2 Exposure on Cement Integrity Under Downhole Conditions

et al. 2015

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The industry is exploring for oil and gas in reservoirs that contain in-situ corrosive fluids, such as CO 2 and H 2 S. In addition, there has been a push to sequester the CO 2 produced from various industrial sources. To this effect, geological carbon dioxide storage is an economically viable method to help reduce greenhouse emissions and CO 2 injection is an effective enhanced oil recovery (EOR) method. Ensuring long-term safety and efficacy is one of the primary technical challenges in this context attributed to potential degradation of the cement sheath, creating pathways for leakage. Design of CO 2 -resistant slurries is an important mitigation approach. This paper discusses an experimental evaluation of the chemical effects of CO 2 on key properties of cement sheaths. Twelve slurries were developed based on the two primary approaches to mitigate CO 2 degradation: (a) reduction of reactive hydration products and (b) reduction of cement matrix permeability. This paper reports results for four selected slurries in a carbonic acid environment. Seven samples of each slurry were cured and then subjected to an aqueous CO 2 environment (carbonic acid) for 15, 30, 90, 180 and 365 days. Downhole conditions were simulated by running the carbonation tests at 165°F and constant CO 2 partial pressure of 2, 000 psi. At the specified time points, samples were removed to perform chemical tests (inductive coupled plasma [ICP], water analysis, X-ray diffraction [XRD], thermogravimetric analysis [TGA], and dye penetration) and physical tests (ultimate compressive strength [UCS], Brinell hardness, permeability, and porosity).The general observation was improvement in terms of physical properties up to 90 days, followed by a decrease that continued throughout the experiment period. Formulations mixed with NaCl brine were additionally degraded by salt leaching. The best resistance to degradation was obtained using formulations with reduced portland content and elastomers to reduce permeability. Higher compressive strength was correlated with low permeability. Most slurries had a permeability lower than 0.1 millidarcy (mD) after one year of exposure.Chemical testing supports the interpretation that the early improvement in physical properties can be attributed to carbonate precipitation, while later degradation is attributed to the formation and leaching of calcium bicarbonate. Some slurries contained sodium chloride in mix water at saturation levels. In which case, sodium chloride leached out of the cement sheath and was confirmed by water analysis. In the carbonic acid (wet) environment, a dense layer of calcium carbonate was observed that corresponded to an increase in Brinell hardness This study demonstrates the efficacy of a testing protocol that can be used to evaluate various cement blends for long-term integrity under downhole conditions and different forms of CO 2 attack. The results were used to design cement systems more resistant to CO 2 degradation than conventional slurries.

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Salt-Tolerant Cement Systems to Mitigate Gelling Effect

Cited by 7 publications

References 7 publications

An Experimental Study on Effects of Static CO2 on Cement under High-Pressure/High-Temperature Conditions

An Experimental Study on Effects of Static CO2 on Cement under High-Pressure/High-Temperature Conditions

Design Procedure for Cementing Intercalated Salt Zones

Long-Term Study of Effects of CO2 Exposure on Cement Integrity Under Downhole Conditions

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