This case study describes the approach taken when drilling an 11 5/8-in. hole section through a salt formation on the Chinarevskoye field in the West Kazakhstan Oblast region where high-intensity brine influxes and subsequent flow had been encountered. The intensity of the brine flow, when encountered, had ranged from 5,000 to 6,000 L/min at an equivalent kick density of 2.2 SG, and it is believed to be among the most intense brine flow experienced in the world during drilling operations. Standard well control measures proved to be inefficient because of the narrow margin between pore pressure and fracture pressure gradients. Several techniques were applied to combat such influxes in a safe manner with minimum associated nonproductive time (NPT). The high-pressured formation in this hole section is associated not only with brine influxes, but also with losses and gas increase scenarios. As a result, the company adopted unconventional drilling techniques with a combination of planned flow-while-drilling (FWD) and mud-cap drilling techniques to reach total depth (TD). These two techniques created a viable and cost-effective solution to mitigate such challenges, helped the company to drill to the planned section TD, and consequently complete the well within the defined authorization for expenditure (AFE) without associated NPT. The paper will cover and emphasize techniques, along with details on running casing and cementing the hole section, which required an unconventional approach for success. The paper will also briefly outline the equipment used, such as rotating control devices (RCDs), a choke manifold, and a separator when drilling this section and their limitations. Despite the complications, the well was successfully drilled, and this experience provided an opportunity for learning. The marked improvements in well control, loss management, and cementation displayed that combining knowledge and experience can reduce the negative impact on well costs when drilling similar cases.

This paper describes the development and field deployment of a new downhole isolation valve system called the Retrievable, Instrumented & Tandem Downhole Deployment Valve (RIT-DDV). The purpose of this technology is to provide a temporary mechanical barrier to isolate and monitor the well during drilling operations in an environment where a full column of single-phase fluid cannot be maintained. The RIT-DDV is based on predominantly used downhole isolation valve (DIV) design and technology, which is a hydraulic flapper-type isolation device installed in the casing that seals the open hole during pipe tripping operations. The key features of the new RIT-DDV systems are dual flapper valves with three downhole pressure and temperature gauges to take measurements above, between, and below the flappers. The advantage of this configuration is that it enhances safety by enabling double-block-and-bleed system functionality, providing valve redundancy, and moreover allowing for continuous real-time monitoring of downhole well conditions. In addition, the RIT-DDV is designed to be reusable and can be tested upon installation and replaced if necessary. The RIT-DDV system enabled the operator to isolate and monitor the well while drilling through a depleted formation that prevented drilling with a full column of single-phase drilling fluid. The RIT-DDV was successfully trialed in western Kazakhstan and demonstrated the potential of this technology to enhance the safety of drilling heavily fractured carbonate formations with reservoir fluids containing hydrogen sulfide (H2S) / carbon dioxide (CO2) that are prone to total loss of circulation. The downhole pressure / temperature monitoring capabilities that the system provides within the casing string helped drill through the depleted fractured carbonate reservoir section without incurring non-productive time (NPT).