Successful Managed Pressure Cementing With Hydraulic Simulations Verification in a Narrow Pore-Frac Pressure Window Using Managed Pressure Drilling in Saudi Arabia

Abstract

Managed pressure operations enable keeping the equivalent circulation density (ECD) within a narrow pore-frac pressure window during drilling and cementing while maintaining the wellbore stability and controlling formation pressures. The operation becomes more complex during a cementing job, where fluids with different density and rheology parameters are pumped downhole at varying rates, resulting in different friction pressure profiles. Proper numerical simulators must be used to model such variations and keep the downhole pressure between the pore and fracture pressures during the operation. Managed pressure techniques and technology were critical to the successful cementation of the 7-in. liner at 12,000 ft. in a gas field in Saudi Arabia, across formations ranging from a high-pressure zone with 2.36 SG (19.65 ppg) formation pore pressure to a depleted low-pressure formation with 2.44 SG (20.32 ppg) fracture pressure. The challenge in this job was to maintain the ECD at 2.40 SG (20 ppg) throughout the cement job to avoid any losses or flow from the formations. An automatic choke setup on the return flow line with a dynamic control system was used to drill the 8.375-in. open hole with KCl polymer mud. Precise cementing simulation was used to determine the ECD during cement placement. Numerous pre-calculations and simulations were run to evaluate various scenarios prior to the cement job to ensure effective manipulation of back pressure through managed pressure drilling (MPD) equipment to maintain ECD at the desired value throughout the cementation process. The detailed simulations run by cementing and MPD engineers prior to the job and a collaborative approach were instrumental in defining a final cementing plan, completing the layout of equipment used for the cementing job, and executing the job with real-time monitoring of all critical parameters affecting ECD and evaluation of the cement job.

A Hydraulic Model for Multiphase Flow Based on the Drift Flux Model in Managed Pressure Drilling

“…When the gas-liquid two-phase flow in the wellbore reaches an equilibrium state, the downhole pressure will decrease less with the increase of drilling fluid displacement, and the time of gas reaching the wellhead will be earlier. (4) The downhole pressure can be controlled by changing the density of drilling fluid. However, the adjustment of drilling fluid density has a serious lag.…”

“…Over the course of drilling, incidents occur frequently and cause various disadvantages, such as longer drilling times, higher costs, and vast risks. Conventional drilling is incapable of addressing these issues, and advanced technology-managed pressure drilling (MPD) is proposed as an alternative, which is useful for resolving complicated situations such as leakage, gas-kick, collapse, and trapping within a narrow density window through reducing the non-productive time and avoiding incidents [3,4]. Regarding offshore drilling, MPD shows remarkable advantages in coping with complex situations and has been widely used in drilling engineering, considering the continued exploration of challenging reservoirs [5,6].…”

Formation interval determination method of MPD based on risk aversion and casing level optimization

“…Managed pressure drilling (MPD) is one of the powerful methods to improve the safety and efficiency of drilling in deep water and deep strata with narrow safe density window [1,2]. With the deepening of oil and gas exploration and development into deep water and complex strata, the number of applications of the MPD technique in the world is increasing year by year [3][4][5]. The feasibility and applicability of the MPD technique in deep water gas fields in the south China sea are also being studied [6,7].…”