Time-Lapse Pulsed Neutron Well Logging in Oil Sands for Monitoring Steam Chamber Development

2021 ◽  
Author(s):  
Yonghwee Kim ◽  
Alexandr Kotov ◽  
David Chace
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Oil Sands ◽  
Extreme Temperature ◽  
Time Lapse ◽  
Well Logging ◽  
Life Cycles ◽  
Temperature Variations ◽  
Steam Chamber ◽  
Pulsed Neutron

Abstract Steam-assisted gravity drainage (SAGD) technology, although a relatively new oil recovery method, has already proved its value in economic development of heavy-oil sands in Western Canada. The SAGD process requires a lifetime monitoring of steam chamber growth to optimize reservoir development, improve oil recovery, and minimize environmental impact. Operators have widely used pulsed neutron well logs to monitor their life cycles of oil sand reservoirs. Time-lapse pulsed neutron logs acquired in observation wells enable operators to effectively track the growth of the steam chamber and identify the changes of formation fluid saturations. We present high-temperature pulsed neutron logging technology and an algorithm to quantify steam, heavy oil and water saturations in SAGD wells. One of the major challenges in well logging operation is to withstand the thermal shock from the steam chamber. Reservoir temperature often varies abruptly, by as much as 250 degrees C in a very short interval, so the logging tool must be stable in drastic temperature variations. Well logging conditions such as a steam-filled wellbore, extra completion hardware and bad cement quality are challenging factors as well. Furthermore, formation fluid saturation analysis in Canadian oil sands is typically complex because the formation water salinity is relatively fresh but varies, clay properties are not homogeneous, and SAGD operations create conditions in which three-phase fluids coexist in the formation. These environmental conditions make it difficult to rely only on commonly used thermal neutron capture cross-section measurements (formation sigma). In this paper, case study examples present the above-mentioned challenges and solutions to identify the multi-component formation fluids. The multi-detector pulsed neutron well logging instrument has been modified with a custom-designed heat flask to handle the extreme temperature variations in the SAGD environment. This heat-flask equipped instrument ensures a stable data acquisition in the presence of rapid and extreme temperature variation and enables a prolonged and time-efficient operation through effective heat management. For saturation analysis, we demonstrate an advanced algorithm to quantify three fluid components using a combination of gamma ray ratio and carbon/oxygen (C/O) measurements.

Remote monitoring of the steam‐flood enhanced oil recovery process

Geophysics ◽  
1987 ◽  
Vol 52 (11) ◽  
pp. 1457-1465 ◽  
Author(s):  
E. F. Laine
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
High Frequency ◽  
Oil Sands ◽  
Seismic Velocity ◽  
Color Image ◽  
Vertical Plane ◽  
Recovery Process ◽  
Steam Flood ◽  
Borehole Seismic

Cross‐borehole seismic velocity and high‐frequency electromagnetic (EM) attenuation data were obtained to construct tomographic images of heavy oil sands in a steam‐flood environment. First‐arrival seismic data were used to construct a tomographic color image of a 10 m by 8 m vertical plane between the two boreholes. Two high‐frequency (17 and 15 MHz) EM transmission tomographs were constructed of a 20 m by 8 m vertical plane. The velocity tomograph clearly shows a shale layer with oil sands above it and below it. The EM tomographs show a more complex geology of oil sands with shale inclusions. The deepest EM tomograph shows the upper part of an active steam zone and suggests steam chanelling just below the shale layer. These results show the detailed structure of the entire plane between boreholes and may provide a better means to understand the process for in situ heavy oil recovery in a steam‐flood environment.

scholarly journals Breccia interlayer effects on steam-assisted gravity drainage performance: experimental and numerical study

2021 ◽  
Author(s):  
Qichen Zhang ◽  
Xiaodong Kang ◽  
Huiqing Liu ◽  
Xiaohu Dong ◽  
Jian Wang
Keyword(s):  
Numerical Simulation ◽  
Oil Recovery ◽  
Oil Sands ◽  
Numerical Study ◽  
Middle Part ◽  
Experimental Results ◽  
Production Performance ◽  
Peak Oil ◽  
Steam Chamber ◽  
The Impact

AbstractCurrently, the reservoir heterogeneity is a serious challenge for developing oil sands with SAGD method. Nexen’s Long Lake SAGD project reported that breccia interlayer was widely distributed in lower and middle part of reservoir, impeding the steam chamber expansion and heated oil drainage. In this paper, two physical experiments were conducted to study the impact of breccia interlayer on development of steam chamber and production performance. Then, a laboratory scale numerical simulation model was established and a history match was conducted based on the 3D experimental results. Finally, the sensitivity analysis of thickness and permeability of breccia layer was performed. The influence mechanism of breccia layer on SAGD performance was analyzed by comparing the temperature profile of steam chamber and production dynamics. The experimental results indicate that the existence of breccia interlayer causes a thinner steam chamber profile and longer time to reach the peak oil rate. And, the ultimate oil recovery reduced 15.8% due to much oil stuck in breccia interlayer areas. The numerical simulation results show that a lower permeability in breccia layer area has a serious adverse impact on oil recovery if the thickness of breccia layer is larger, whereas the effect of permeability on SAGD performance is limited when the breccia layer is thinner. Besides, a thicker breccia layer can increase the time required to reach the peak oil rate, but has a little impact on the ultimate oil recovery.

An Investigation Into Propagation Behavior of the Steam Chamber During Expanding-Solvent SAGP (ES-SAGP)

SPE Journal ◽  
2019 ◽  
Vol 24 (02) ◽  
pp. 413-430
Author(s):  
Zhanxi Pang ◽  
Lei Wang ◽  
Zhengbin Wu ◽  
Xue Wang
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Physical Simulation ◽  
Heat Losses ◽  
Oil Reservoirs ◽  
Oil Viscosity ◽  
Sweep Efficiency ◽  
Experimental Conditions ◽  
Steam Chamber ◽  
Heavy Oil Reservoirs

Summary Steam-assisted gravity drainage (SAGD) and steam and gas push (SAGP) are used commercially to recover bitumen from oil sands, but for thin heavy-oil reservoirs, the recovery is lower because of larger heat losses through caprock and poorer oil mobility under reservoir conditions. A new enhanced-oil-recovery (EOR) method, expanding-solvent SAGP (ES-SAGP), is introduced to develop thin heavy-oil reservoirs. In ES-SAGP, noncondensate gas and vaporizable solvent are injected with steam into the steam chamber during SAGD. We used a 3D physical simulation scale to research the effectiveness of ES-SAGP and to analyze the propagation mechanisms of the steam chamber during ES-SAGP. Under the same experimental conditions, we conducted a contrast analysis between SAGP and ES-SAGP to study the expanding characteristics of the steam chamber, the sweep efficiency of the steam chamber, and the ultimate oil recovery. The experimental results show that the steam chamber gradually becomes an ellipse shape during SAGP. However, during ES-SAGP, noncondensate gas and a vaporizable solvent gather at the reservoir top to decrease heat losses, and oil viscosity near the condensate layer of the steam chamber is largely decreased by hot steam and by solvent, making the boundary of the steam chamber vertical and gradually a similar, rectangular shape. As in SAGD, during ES-SAGP, the expansion mechanism of the steam chamber can be divided into three stages: the ascent stage, the horizontal-expansion stage, and the descent stage. In the ascent stage, the time needed is shorter during ES-SAGP than during SAGP. However, the other two stages take more time during nitrogen, solvent, and steam injection to enlarge the cross-sectional area of the bottom of the steam chamber. For the conditions in our experiments, when the instantaneous oil/steam ratio is lower than 0.1, the corresponding oil recovery is 51.11%, which is 7.04% higher than in SAGP. Therefore, during ES-SAGP, not only is the volume of the steam chamber sharply enlarged, but the sweep efficiency and the ultimate oil recovery are also remarkably improved.

Geomechanical Effects on the SAGD Process

2007 ◽  
Vol 10 (04) ◽  
pp. 367-375 ◽  
Author(s):  
Patrick Michael Collins
Keyword(s):  
Heavy Oil ◽  
Growth Pattern ◽  
Oil Sands ◽  
Elevated Temperatures ◽  
Design Stage ◽  
Western Canada ◽  
Oil Sand ◽  
Confining Stress ◽  
Steam Chamber ◽  
Elevated Pressures

Summary Steam-assisted gravity drainage (SAGD) is a robust thermal process that has revolutionized the economic recovery of heavy oil and bitumen from the immense oil-sands deposits in western Canada, which have 1.6 to 2.5 trillion bbl of oil in place. With steam injection, reservoir pressures and temperatures are raised. These elevated pressures and temperatures alter the rock stresses sufficiently to cause shear failure within and beyond the growing steam chamber. The associated increases in porosity, permeability, and water transmissibility accelerate the process. Pressures ahead of the steam chamber are substantially increased, promoting future growth of the steam chamber. A methodology for determining the optimum injection pressure for geomechanical enhancement is presented that allows operators to customize steam pressures to their reservoirs. In response, these geomechanical enhancements of porosity, permeability, and mobility alter the growth pattern of the steam chamber. The stresses in the rock will determine the directionality of the steam chamber growth; these are largely a function of the reservoir depth and tectonic loading. By anticipating the SAGD growth pattern, operators can optimize on the orientation and spacing of their wells. Core tests are essential for the determination of reservoir properties, yet oil sand core disturbance is endemic. Most core results are invalid, given the high core-disturbance results in test specimens. Discussion on the causes and mitigation of core disturbance is presented. Monitoring of the SAGD process is central to understanding where the process has been successful. Methods of monitoring the steam chamber are presented, including the use of satellite radar interferometry. Monitoring is particularly important to ensure caprock integrity because it is paramount that SAGD operations be contained within the reservoir. There are several quarter-billion-dollar SAGD projects in western Canada that are currently in the design stage. It is essential that these designs use a fuller understanding of the SAGD process to optimize well placement and facilities design. Only by including the interaction of SAGD and geomechanics can we achieve a more complete understanding of the process. Introduction Geomechanics examines the engineering behavior of rock formations under existing and imposed stress conditions. SAGD imposes elevated pressures and temperatures on the reservoir, which then has a geomechanical response. Typically, the SAGD process is used in unconsolidated sandstone reservoirs with very heavy oil or bitumen. In-situ viscosities can exceed 5 000 000 mPa•s [mPa•s º cp] under reservoir conditions. These bituminous unconsolidated sandstones, or "oil sands," are unique engineering materials for two reasons. Firstly, the bitumen is essentially a solid under virgin conditions, and secondly, the sands themselves are not loosely packed beach sands. Instead, they have a dense, interlocked structure that developed as a result of deeper burial and elevated temperatures over geological time. In western Canada, the silica pressure dissolution and redeposition over 120 million years developed numerous concave-convex grain contacts (Dusseault 1980a; Touhidi-Baghini 1998) in response to the additional rock overburden and elevated temperatures. As such, these oil sands are at a density far in excess of that expected under current or previous overburden stresses. Furthermore, once oil sands are disturbed, the grain rotations and dislocations preclude any return to their undisturbed state. Oil sands, by definition, have little to no cementation. As such, their strength is entirely dependent upon grain-to-grain contacts, which are considerable in their undisturbed state. These contacts are maintained by the effective confining stress. Any reduction in the effective confining stress will result in a reduction in strength. Because the SAGD process increases the formation fluid pressure, it reduces the effective stresses and weakens the oil sand.

Feasibility of time-lapse gravity and gravity gradiometry monitoring for steam-assisted gravity drainage reservoirs

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. WA99-WA111 ◽  
Author(s):  
Anya Reitz ◽  
Richard Krahenbuhl ◽  
Yaoguo Li
Keyword(s):  
Heavy Oil ◽  
Production Efficiency ◽  
Low Cost ◽  
Time Lapse ◽  
Gravity Drainage ◽  
Great Success ◽  
Gravity Gradiometry ◽  
Steam Chamber ◽  
Steam Assisted Gravity Drainage ◽  
The Cost

There is presently an increased need to monitor production efficiency as heavy oil reservoirs become more economically viable. We present a feasibility study of monitoring steam-assisted gravity drainage (SAGD) reservoirs using time-lapse gravimetry and gravity gradiometry. Even though time-lapse seismic has historically shown great success for SAGD monitoring, the gravimetry and gravity gradiometry methods offer a low-cost interseismic alternative that can complement the seismic method, increase the survey frequency, and decrease the cost of monitoring. In addition, both gravity-based methods are directly sensitive to the density changes that occur as a result of the replacement of heavy oil by steam. Advances in technologies have made both methods viable candidates for consideration in time-lapse reservoir monitoring, and we have numerically evaluated their potential application in monitoring SAGD production. The results indicate that SAGD production should produce a strong anomaly for both methods at typical SAGD reservoir depths. However, the level of detail for steam-chamber geometries and separations that can be recovered from the gravimetry and gravity gradiometry data is site dependent. Gravity gradiometry shows improved monitoring ability, such as better recovery of nonuniform steam movement due to reservoir heterogeneity, at shallower production reservoirs. Gravimetry has the ability to detect SAGD steam-chamber growth to greater depths than does gravity gradiometry, although with decreasing resolution of the expanding steam chambers.

Pressure and temperature dependence of acoustic wave speeds in bitumen-saturated carbonates: Implications for seismic monitoring of the Grosmont Formation

Geophysics ◽  
2017 ◽  
Vol 82 (5) ◽  
pp. MR133-MR151 ◽  
Author(s):  
Arif Rabbani ◽  
Douglas R. Schmitt ◽  
Jason Nycz ◽  
Ken Gray
Keyword(s):  
Oil Recovery ◽  
Oil Sands ◽  
Saturation Pressure ◽  
Time Lapse ◽  
S Wave ◽  
Heated Sample ◽  
Wave Speeds ◽  
Seismic Reflectivity ◽  
Water Saturated ◽  
Northern Alberta

Recent time-lapse seismic observations in carbonate reservoirs subject to steam-assisted enhanced oil recovery display substantial changes in seismic reflectivity due to the combined effects of saturation, pressure, and temperature. Understanding these field seismic observations requires knowledge of the effects on the seismic wave speeds in bitumen-saturated carbonates. We have conducted ultrasonic measurements of P- and S-wave velocities in bitumen-saturated dolomite taken from the Grosmont Formation in northern Alberta. Wave speeds are measured under a variety of conditions of constant pore pressure, constant effective pressure, and with varying temperature to map the various controlling factors. The temperature-dependent declines of 12% and 9% for the P- and S-wave speeds, respectively, with temperatures from 10°C to 102°C are most notable. Unlike oil sands, at times, the dolomite retains its structure upon removal of the bitumen allowing for measurement of the dry and water-saturated frame properties and their subsequent use in substitutional modeling. None of the standard bounding, inclusion, or Biot-Gassmann family models adequately describe the observations in the heated sample. The deviations may be in part due to the inability of these models to properly incorporate the complex bitumen non-Newtonian rheology including a bulk viscosity.

scholarly journals Description of steam chamber shape in heavy oil recovery using 4D microgravity measurement technology

2013 ◽  
Vol 40 (3) ◽  
pp. 409-412 ◽  
Author(s):  
Yujun LI ◽  
Fangxiang REN ◽  
Liqiang YANG ◽  
Dasheng ZHOU ◽  
Xin TIAN
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Measurement Technology ◽  
Heavy Oil Recovery ◽  
Steam Chamber

Seismic characterization of heavy oil reservoir during thermal production: A case study

Geophysics ◽  
2017 ◽  
Vol 82 (1) ◽  
pp. B13-B27 ◽  
Author(s):  
Hemin Yuan ◽  
De-Hua Han ◽  
Weimin Zhang
Keyword(s):  
Heavy Oil ◽  
Rock Physics ◽  
Time Lapse ◽  
Steam Injection ◽  
Oil Reservoirs ◽  
Inversion Method ◽  
Oil Reservoir ◽  
Steam Chamber ◽  
Heavy Oil Reservoirs ◽  
Heavy Oil Reservoir

Heavy oil reservoirs are important alternative energy resources to conventional oil and gas reservoirs. However, due to the high viscosity, most production methods of heavy oil reservoirs involve thermal production. Heavy oil reservoirs’ properties change dramatically during thermal production because the viscosity drops drastically with increasing temperature. Moreover, the velocity and density also decrease after steam injection, leading to a longer traveltime of seismic velocities and low impedance of the steam chamber zone. These changes of properties can act as indicators of the steam chamber and can be detected through the time-lapse inversion method. We first establish the rock-physics relationship between oil sands’ impedance and temperature on the basis of our previous laboratory work. Then, we perform the forward modeling of the heavy oil reservoir with the steam chamber to demonstrate the influence of steam injection on seismic profiles. Then, we develop a modified-Cauchy prior-distribution-based time-lapse inversion method and perform a 2D model test. The inversion method is then applied on the real field data, and the results are analyzed. By combining the inverted impedance and rock-physics relation between impedance and temperature, the temperature distribution map is obtained, which can work as an indicator of steam chamber. Finally, an empirical relation between impedance and velocity is established, and velocity is derived from the impedance.

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