The use of foamed cement systems for deepwater applications has been increasing and is often the system of choice for shallow hazard mitigation as in the Gulf of Mexico. However, there is little information regarding foamed cement behavior under wellbore conditions. Research is being conducted to develop a predictive relationship between the mesostructure and physical properties of foamed cements used in offshore applications. Samples of foamed cement have been generated using both atmospheric laboratory and high-pressure field preparation methods. Field-generated foamed cement samples were collected in constant pressure (CP) sample cylinders using the same full-scale field equipment used to generate foamed cements in a well. These samples were scanned while inside the CP cylinders using X-ray Computed Tomography with a scan resolution of approximately 35 m.Results of the laboratory testing indicate a correlation between foam quality, bubble size distribution and physical properties such as strength and permeability. Initial results also highlight key differences in laboratory and field-generated foamed cements. The variations in cement structure within the fieldgenerated foamed cement samples appear to indicate a strong relationship between the flow of the cement into the sample vessel and the final porosity and properties of the in-place hardened cement. This research will provide a better understanding of the effects that foam cement production, transport downhole, and delivery to the wellbore annulus has on the overall sealing process.

The objective of this paper is to evaluate the dynamic moduli of atmospheric generated foamed cements at varying foam qualities routinely used for zonal isolation during well construction. Mechanical properties of the hardened foamed cement samples, such as Young's modulus (YM) and Poisson's ratio (PR) will be discussed, as well as permeability. All of these properties were obtained as a function of cyclic confining pressure ranging from 12 -52 MPa (1,740 -7,540-psi). The dynamic parameters were derived from ultrasonic velocity measurements, while permeability was measured using the transient method. Stepwise loading and unloading schedules were conducted to test the permeability and mechanical properties of the foamed cement at simulated wellbore conditions. Applied pressures varied between 6.5 MPa (943 psi) to 46.5 Ma (6,744 psi) in 4 MPa (580 psi) increments in two full up/down cycles. At every increment during these cycles, ultrasonic compressional (P), fast shear (S1), and slow shear (S2) wave velocities were measured, as well as the samples' response to the upstream sine pressure wave of approximately 0.5 MPa amplitude. From the sonic velocity data the dynamic moduli including YM and PR were calculated, while the sample's response to the pressure wave was used for permeability calculations. Observations of both neat and foamed samples reveal variations in YM as well as changes in the other properties and characteristics. Differences were observed between the foam qualities, depending on the parameter being assessed. This information should enable design contingencies and allow for more resilient designs of foamed cements when used during well construction. In addition, industry can use these results as a baseline for comparison with previous, current, or future work including recently acquired field-generated foamed cement samples (Kutchko et al., 2014).

Saudi Aramco faces a wide array of challenges maintaining wellbore stability during drilling and primary cementing operations. As a result, it has implemented revised strategies and methods to remediate losses during well construction operations. The origin of these strategies, swith some adopted from deepwater operations, has led to improved zonal isolation and operational efficiencies. The conventional methods used to cure losses during drilling with cement plugs can be inefficient usually requiring multiple attempts with mixed success. A revised method focuses on hydrostatics of the cementing fluids as well as advanced placement methods based upon the loss circulation boundary conditions to improve the plug success rate. During primary cementing across multiple zones with risks ranging from ultra-high permeability, low bottom hole pressures, and highly natural fractured carbonates, the risk of losses during cement placement has led to inconsistent zonal isolation. A revised strategy for the cementing fluids used during primary cementing based upon these same risks will demonstrate the improved zonal isolation success. The manuscript details the methods, strategies, and case histories discussed above.

In certain regions of oil and gas operations, lost circulation is a common occurrence, especially when a majority of the openhole exposed during primary cementing is carbonate-based formations. This can lead to lost circulation risks in most applications. To overcome lost circulation risks during primary cementing, a new tailored spacer system shows to improve the cement placement success. The manuscript discusses the quality assurance and performance testing with field cases demonstrating the value contributions of the spacer for achieving zonal isolation requirements as well as the top of cement objectives. The work efforts presented shows a spacer meeting and sometimes showing incremental wellbore strengthening in comparison to the published literature for existing available spacers used to overcome similar lost circulation risks.

Drilling operations are presented with challenges for both normal and complex wellbore environments with a focus on minimizing nonproductive time while successfully achieving the well objectives. In some cases, it is likely to reach the well objectives and remedial cementing may play a significant part whether it is due to exploration or wildcat-type wells, complex well construction, or the geological uncertainties. As a necessary evil, being able to plan for contingencies and success when faced with remedial cementing applications can reduce the potential replication of treatments and improve the extent of nonproductive time. When these situations arise during deepwater operations, there are challenges beyond the traditional cementing scope of work such as multiple temperature and pressure gradients, subsea equipment, and large-bore tubulars. Drilling deeper these factors may also include lithology, wellhead clearances, stuck pipe, failure of barriers, and/or an unstable well. Furthermore, traditional service tools find limited success with remedial operations in large-bore casing/tubulars, often requiring alternative solutions, including pumping through bottom hole assemblies, using inflatable packers, and developing other non-traditional placement techniques. This paper will present methods to improve the success of cement placement while performing remedial cementing operations in an effort to reduce nonproductive time and execute common contingency planning. In addition, specific well situations and events executing these methods will demonstrate the impacts to remediate the necessary evil.