Real-Time Monitoring of Piezoresistive Smart Cement To Verify Operations
- Adam Wilson (JPT Special Publications Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- May 2017
- Document Type
- Journal Paper
- 79 - 80
- 2016. Offshore Technology Conference
- 1 in the last 30 days
- 82 since 2007
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This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 27060, “Field Test for Real-Time Monitoring of Piezoresistive Smart Cement To Verify Cementing Operations,” by C. Vipulanandan, M. Ali, B. Basirat, A. Reddy, N. Amin, and A. Mohammed, University of Houston; S. Dighe, SPE, Baker Hughes; and H. Farzam, Cemex, prepared for the 2016 Offshore Technology Conference, Houston, 2–5 May. The paper has not been peer reviewed. Copyright 2016 Offshore Technology Conference. Reproduced by permission.
A field well was designed, built, and used to demonstrate the concept of real-time monitoring of the flow of drilling mud and smart cement and the hardening of the cement in place. A new method has been developed to measure the electrical resistivity of the materials with the two-probe method. Using the new concept, it has been proved that resistivity dominated the behavior of drilling fluid and smart cement.
With reported failures and growing interest in environmental and economic concerns in the oil and gas industry, integrity of the cement sheath is of major importance. Oilwell cement serves many purposes in cemented oil and gas wells. Foremost among these is to form a sealing layer between the well casing and the geological formation.
In order to characterize the cement and cement concrete in various applications, electrical-resistivity measurement has been used by many researchers. Studies have also examined the piezo-resistive behavior of modified cement-based and polymer composites. One conclusion is that the change in resistivity has the potential to be used to determine the integrity of the materials.
Smart Oilwell Cement
Cement-slurry flow and stability are the major requirements in well cementing. Oil- and gas-well cements are usually made from Portland cement clinker or from blended hydraulic cements. When admixtures are used with cement, tensile and flexural properties are modified. Also, admixtures will have an effect on the rheology, corrosion resistance, shrinkage, thermal conductivity, specific heat, electrical conductivity, and absorption (heat and energy) properties of cement.
A smart cement has been developed that can sense any changes going on inside the borehole during cementing and during curing after the cementing job. The smart cement can sense the changes in the water/cement ratio, different additives, and any pressure applied to the cement sheath in terms of piezo resistivity. The failure compressive strain for the smart cement was 0.2% at peak compressive stress, and the resistivity change is on the order of several hundreds, making it more than 500 times more sensitive.
Theory and Concept
Impedance Model. Equivalent Circuit. It is important to identify the most appropriate equivalent circuit to represent the electrical properties of a material to characterize its performance with time. In this study, different possible equivalent circuits were analyzed to find an appropriate equivalent circuit to represent smart cement and drilling fluid.
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