This work investigates a 3400m thick Tertiary succession from the prolific Gabo hydrocarbon field in the Niger Delta and presents a well-scale geomechanical model to address the pore pressure, borehole stability and fault slip potential attributes. The Tertiray stratigraphy is dominated by cyclic clastic sedimentation and it produces hydrocarbon from the Eocene Agbada Formation. An average vertical stress gradient of 0.85-0.90 PSI/feet is interpreted from the density logs. Extensive direct downhole measurements indicate a sub-hydrostatic pressure gradient of 0.325 PSI/feet in the Upper Agbada reservoir sands, while the lower producers are presently in hydrostatic regime (0.435 PSI/feet). Pore pressure against the shales are estimated by Eaton’s disequilibrium compaction method, which are found to be mildly overpressured (0.49 PSI/feet). The minimum horizontal stress (S_hmin) gradient ranges between 0.59 and 0.70 PSI/feet. Wellbore stability is addressed by the Mohr-Coulomb failure model and the assessed failures are corroborated with the caliper log observations. Drilling mud weight used in the studied wells were found to be less than the shale collapse pressure gradient, resulting in selective wellbore over-gauging in the Eocene shales, intercalated with the sandstone reservoir intervals. Safe and effective downhole pressure window is inferred from the interpreted pore pressure, collapse pressure and S_hmin to avoid any kick, loss or compressive wellbore failures by optimum mud weight designing. Inferences on drilling optimization are discussed which will be helpful for better planning of the infill injector wells. A fault slip analysis indicates that pore pressure could be increased by 1100-1200 PSI during the repressurization in the Upper and Lower Agbada reservoirs without inducing reservoir instabilities as well as caprock failure.

这项工作研究了尼日尔三角洲多产的Gabo油气田3400m厚的第三系演替，并提出了一个井眼规模的地质力学模型，以解决孔隙压力，井眼稳定性和断层滑动潜力的属性。Tertiray地层以周期性碎屑沉积为主，并由始新世的Agbada组产生碳氢化合物。从密度测井可以得出平均垂直应力梯度为0.85-0.90 PSI /英尺。广泛的直接井下测量表明，上阿格巴达油藏砂岩的亚静水压力梯度为0.325 PSI /英尺，而下层生产者目前处于静水状态（0.435 PSI /英尺）。用伊顿不平衡压实法估算页岩上的孔隙压力，发现该压力略有过压（0.49 PSI /英尺）。_hmin）梯度范围介于0.59和0.70 PSI /英尺之间。井眼稳定性由Mohr-Coulomb破坏模型解决，评估的破坏与卡尺测井观测结果相符。研究井中使用的钻探泥浆重量小于页岩坍塌压力梯度，导致始新世页岩中选择性井眼超限，并夹有砂岩储层间隔。从解释的孔隙压力，崩塌压力和S _hmin推断出安全有效的井下压力窗口通过优化泥浆重量设计来避免任何反冲，损失或井眼压缩故障。讨论了钻探优化的推论，这将有助于更好地规划注入井。断层滑动分析表明，在上，下阿格巴达油藏增压过程中，孔隙压力可能会增加1100-1200 PSI，而不会引起油藏不稳定性和盖层破裂。