Extending the Range of Cement Evaluation

Abstract

AbstractWell integrity assurance and zonal isolation, are the main pillars for any oil and gas well, it was a practice in the past to evaluate cement behind casings for casings smaller than 13 3/8 inch, however with the increase in drilling deeper and more challenging wells, the need for evaluating cement behind larger and thicker casings became a necessity.Different logging companies have invested in their existing cement evaluation services and upgraded their tool designs, specifications, and increased tool operating range to address the larger and thicker casing requirements. By mid-2016, the upgraded tool measurements range was extended to evaluate up to 22-inch.KOC in South-East asset started developing their Marrat deep reservoir back in 2018, these wells are designed with large surface casings ranging between (18 5/8-inch and 24-inch) across their main reservoirs (Burgan) and the shallow water and gas bearing formations (Dammam, Radhuma, Tayarat, and Mishrif). Dammam, Radhuma, Tayarat, and Mishrif formations, feature a highly fractured carbonate reservoir and comprise corrosive water and trapped gas pockets. The corrosive water and the trapped gas pockets pose future potential well integrity risks in the field, which implies the need for proper zonal isolation throughout the well and the field lifespan. These formations also comprise a low formation frac gradient, that raises the requirement for low-density cement ranging from 8.5 to 10.5 PPG to overcome the shallow loss zone.The newly developed extended range for the ultrasonic cement evaluation tools can cover up to 18 5/8 inch surface casings for KOC, however, some additional tests, work, and modifications were required to accommodate the 24-inch casing, which will be discussed later in this paper.