Cement samples are kept after pumping cement in oil well operations for several important reasons. The two images below shoes cement samples, one collected while cement is in liquid phase and another one is when cement is set for awhile.
Cement Sample in Liquid Phase
Cement Sample After Set
Cementing operations in the oil and gas industry are a critical component of well construction and integrity. Proper casing and cementing hardware play a crucial role in ensuring the successful execution of these operations. In this article, we will explore the various equipment used in cementing operations, including guide shoes, float collars, centralizers, cement wiper plugs, and multi-stage collars.
casing and cement hardware
Guide Shoes and Float Shoes: Continue reading
Cementing in the oil and gas industry involves a meticulous process, and cementing additives play a crucial role in fine-tuning the properties of cement slurries. These additives are carefully selected to control slurry density, rheology (flow behavior), fluid loss, and to impart specialized characteristics for effective cement placement in diverse downhole conditions. Let’s explore the various categories of additives used in cementing:
1. Accelerators: Accelerators are chemicals employed to expedite the thickening process of a cement slurry and enhance early strength development. Typically used in conductor and surface casing applications to reduce waiting-on-cement time (WOC), common accelerators include calcium chloride (CaCl2), sodium chloride (NaCl), and seawater. Continue reading
Oil well cement adheres to API Specification 10 and is categorized into eight classes, labeled A to H, based on its specific properties. Among these, Class G and Class H serve as foundational well cements that can be employed alongside accelerators and retarders to accommodate a broad spectrum of well depths and temperature conditions. One notable distinction between these two classes lies in their particle size, with Class H being notably coarser than Class G.
When cement is in transition period (forming the bond), you will lose some hydrostatic pressure because cement becomes solid phase, therefore only water in the cement will provide hydrostatic pressure. In many cases happened, there is no issue while performing the cement job, however; once the cement is set after period of time, there is a casing pressure indicating that there is hydrocarbon in the annulus.
This example will demonstrate you why the well is in underbalance condition while waiting on cement.
Well information: Previous 9-5/8” casing shoe at 4000’ ft.
The vertical well (8.5” hole) is drilled to TD at 10,000ft with 12.1 ppg mud and the pay zone is at 9,800’ TVD with reservoir pressure of 11.6 ppg. The cement is planned to cover 3,500 ft in the annulus above the casing shoe. Water used to mix cement is 8.3 ppg weight.
