Moderate Collapse in a Shale Cap of a Nearly Depleted Reservoir

Zhao, Kai; Han, Jie; Dou, Liangbin; Feng, Yongcun

doi:10.3390/en10111820

Cited by 2 publications

(3 citation statements)

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“…where ω is the half of the tolerable breakout width, ( • ). In general, the breakout occurs as a series of successive spalls along the direction of the minimum principal horizontal stress and results from shear failure subparallel to the free wall of the borehole [2,6,28,[32][33][34][35][36][37]. As shown in Figure 5, where 1 , 2 and 3 represent the breakout zones during deepening.…”

Section: Breakout Width Modelmentioning

confidence: 99%

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Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Tang

Chen

et al. 2019

Energies

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Due to the uncertainty of formation properties and improper wellbore stability analysis methods, the input parameters are often uncertain and the required mud weight to prevent wellbore collapse is too large, which might cause an incorrect result. However, the uncertainty evaluation of input parameters and their influence on safe mud weight window (SMWW) is seldom investigated. Therefore, the present paper aims to propose an uncertain evaluation method to evaluate the uncertainty of SMWW. The reliability assessment theory was introduced, and the uncertain SMWW model was proposed by involving the tolerable breakout, the Mogi-Coulomb (MG-C) criterion and the reliability assessment theory. The influence of uncertain parameters on wellbore collapse, wellbore fracture and SMWW were systematically simulated and investigated by utilizing Monte Carlo simulation. Finally, the field observation of well SC-101X was reported and discussed. The results indicated that the MG-C criterion and tolerable breakout is recommended for wellbore stability analysis. The higher the coefficient of variance is, the higher the level of uncertainty is, the larger the impact on SMWW will be, and the higher the risk of well kick, wellbore collapse and fracture will be. The uncertainty of basic parameters has a very significant impact on SMWW, and it cannot be ignored. For well SC-101X, the SMWW predicted by analytical solution is 0.9921–1.6020 g/cm3, compared to the SMWW estimated by the reliability assessment method, the reliability assessment method tends to give a very narrow SMWW of 1.0756–1.0935 g/cm3 and its probability is only 80%, and the field observation for well kick and wellbore fracture verified the analysis results. For narrow SMWW formation drilling, some kinds of advanced technology, such as the underbalanced drilling (UBD), managed pressure drilling (MPD), micro-flow drilling (MFD) and wider the SMWW, can be utilized to maintain drilling safety.

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Section: Breakout Width Modelmentioning

confidence: 99%

“…According to Equations (30)- (33), the EMWFP is usually depended on the maximum horizontal stress (σ H ), the minimum horizontal stress (σ h ), the pore pressure (p p ), the Biot's coefficient (α), and the tensile strength (S t ). The influence of the mean value of each basic parameter is a key aspect to EMWFP.…”

Section: Influence Of Mean Valuementioning

confidence: 99%

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Tang

Chen

et al. 2019

Energies

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“…Although the platform is located in the newly developing reservoirs, some ERWs may target depleted reservoirs which are considered counterproductive with additional platforms. However, there is a Maximum Allowable Measured Depth (MAMD) to allow conventional drilling as the operating window should remain within the safe mud weight window between fracture pressure gradient and pore pressure gradient or collapse pressure gradient [2,11,12]. In extended-reach drilling targeting to depleted reservoirs, the fracture pressure gradient may be significantly reduced and collapse pressure gradient would be increased in some directions [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

The Maximum-Allowable Well Depth While Drilling of Extended-Reach Wells Targeting to Offshore Depleted Reservoirs

et al. 2018

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In depleted offshore reservoirs, pore pressure declines and consequently horizontal in-situ stresses decrease as well. This causes a very limited well depth for extended-reach drilling targeting to offshore depleted reservoirs. In this paper, based on analyzing the safe mud weight window of the depleted offshore reservoirs, a model of predicting the Maximum Allowable Measured Depth (MAMD) for extended-reach drilling targeting to offshore depleted reservoirs is developed. Meanwhile, the numerical method of the model is proposed, and the key affecting factors of the MAMD are also investigated. The results show the pore pressure depletion has obvious effects on the MAMD. With the depletion of pore pressure, the safe mud weight window appears narrower and even disappears, consequently the predicted MAMD becomes shorter. For a normal regime depositional environment in the depleted reservoirs, it may be impossible to drill with conventional drilling method in the nearby directions of the maximum horizontal in-situ stress, while it may be much safer and attain a long MAMD when drilling in the directions near the minimum horizontal in-situ stress. Moreover, the MAMD will decrease with the increase of Poisson's ratio and Biot's parameter, and its response to Poisson's ratio is more obvious. For a specific target depleted reservoir, the extended-reach drilling with a high borehole inclination may have a longer MAMD than that with a low borehole inclination. This paper presents a method for promoting the design of extended-reach drilling targeting to offshore depleted reservoirs.

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Moderate Collapse in a Shale Cap of a Nearly Depleted Reservoir

Cited by 2 publications

References 41 publications

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method

The Maximum-Allowable Well Depth While Drilling of Extended-Reach Wells Targeting to Offshore Depleted Reservoirs

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