Real-Time Pore Pressure Detection: Indicators and Improved Methods

Abstract

High uncertainties may exist in the predrill pore pressure prediction in new prospects and deepwater subsalt wells; therefore, realtime pore pressure detection is highly needed to reduce drilling risks. The methods for pore pressure detection (the resistivity, sonic, and corrected -exponent methods) are improved using the depth-dependent normal compaction equations to adapt to the requirements of the real-time monitoring. A new method is proposed to calculate pore pressure from the connection gas or elevated background gas, which can be used for real-time pore pressure detection. The pore pressure detection using the logging-whiledrilling, measurement-while-drilling, and mud logging data is also implemented and evaluated. Abnormal pore pressure indicators from the well logs, mud logs, and wellbore instability events are identified and analyzed to interpret abnormal pore pressures for guiding real-time drilling decisions. The principles for identifying abnormal pressure indicators are proposed to improve real-time pore pressure monitoring.

Geological characteristics and abnormal pore pressure prediction in shale oil formations of the Dongying depression, China

“…Since rock properties change greatly from smectite to illite (as illustrated in Section 3.3), it should use two different normal compaction trendlines or a composite one for pore pressure prediction . Otherwise, if only the illite normal compaction trendline is used for pore pressure prediction, the shallow pore pressure will be overestimated, particularly if this normal compaction trend is calibrated by measured pore pressures in the deep formations.…”

Study and Verification of a Physical Simulation System for Formation Pressure Testing while Drilling

“…(2) Pore pressure detection during drilling: pore pressure can be detected by using drilling parameters, the theoretical basis is still the normal compaction theory, where the rate of penetration (ROP) data is used to determine NCT, and the most commonly used methods include the d c -exponent method and sigma exponent method [5,6], but the detection precision is very poor.…”

“…In general, the normal pore pressure increases with depth at a constant gradient (i.e., the hydrostatic pressure gradient); if the pore pressure is lower or higher than the hydrostatic pressure or normal formation pressure, it is an abnormal pore pressure [3,4]. When the pore pressure is higher than the normal pore pressure, it is overpressure or abnormal high pore pressure; while when the pore pressure is lower than the normal pore pressure, it is underpressure or subnormal pore pressure [5,6]. The abnormal pore pressure has so many impacts on the exploration, exploitation, and utilization activities of deep earth geo-energy and geo-resources, such as the petroleum drilling, scientific drilling, petroleum exploitation, geothermal exploitation, CO 2 geological sequestration, and nuclear waste disposal [7][8][9][10][11].…”

“…In the process of petroleum drilling and scientific drilling, pore pressure is one of the most important parameters for the drilling plan; it can be used to optimize the drilling fluid density, wellbore configuration, and pressure control equipment. If the abnormal pore pressure cannot be accurately predicted, some very complex down-hole incidents, such as fluid influx, gas kick, overflow, blowout, and mud loss, can occur and even occur the out-of-control blowout and lost circulation in a severe case, which obviously increase the drilling risk, cycle, and costs [5,6]. In the process of petroleum exploitation, pore pressure is an important basic parameter for oil and gas development; it can be used to characterize the type of reservoir, estimate geological reserves, determine the energy of oil and gas reservoir, and conduct the prediction of production performance, which determines the formation fluid properties, the development mode, and the ultimate recovery [12].…”

“…Currently, there are five kinds of conventional methods that can be used to determine formation pressure, such as the seismic method, d c -exponent method, well logging method, drill stem test (DST), and wire-line formation test (WFT) [5,6]. However, these methods are usually featured by low precision and poor real time, which makes accurately detecting formation pressure in real time become very difficult.…”