Sequential Prediction of Drilling Fluid Loss Using Support Vector Machine and Decision Tree Methods

Machine learning methods have been applied to predict depths of fluid loss in hydrocarbon exploration.During drilling, lost circulation can be described as the unpleasant loss of all or part of drilling mud or fluid into the immediate formations or affected formation by excessive hydrostatic pressure, sufficient to fracture the formation or expand existing fractures encountered during the drilling process. In this study, we deployed Python codes of Support Vector Machine (SVM) and Decision Tree (DT) methodsto categorical data obtained from drilling operations in a producing field to predict lost circulation occurrence. The modelsleveraged the capability of both SVM and DT to achieve binary classification by adopting flow-out percentage of less than 70 percent as the points of lost circulation. That is, 70% represented asNo Loss. Prediction models were applied to 10 input variables preprocessed with principal component analysis (PCA) to reduce dimensionality and focus on essential variables. The preprocessed SVM model gave an improved result while preprocessing does not affect DT models. Overall, DT models predicted accurate fluid losszones and can be scaled up to field operations with options ofcontinuous sampled variables

Multifractal characterization of the Coniacian–Santonian OAE3 in lacustrine and marine deposits based on spectral gamma ray logs

Abstract Limited to the Atlantic and its surrounding basins, the expression of the Coniacian–Santonian oceanic anoxic event (OAE3) was discovered in the non-marine Cretaceous Songliao Basin, Eastern Asia not long ago. In this study, based on spectral gamma ray logs data recorded in three basins, the self-similarity of the OAE3 was studied through the analysis of the scaling properties of thorium–potassium and thorium–uranium distributions both in marine and terrestrial environments using the multifractal detrending fluctuation analysis. The results indicate that, in both marine and terrestrial systems, the OAE3 intervals are characterized by their multifractal nature due to long-range correlation. However, the multifractal features of the studied OAE3 intervals are different in the three basins, although some common trends were observed. By comparing the degree of multifractality of the OAE3 deposits with the clay minerals and the redox conditions, it appears that the changes of the multifractal features are controlled by local changes such as clay mineralogy and redox conditions in both milieus under different sedimentation patterns. At all sites, the left side shortened spectrum of the thorium–potassium distribution suggests the presence of local fluctuations with minor amplitudes during the OAE3. Furthermore, the shortened singularity spectrum of the thorium–uranium distribution reflects the existence of small-scale fluctuations with large amplitudes at marine sites while in the non-marine Songliao Basin, the thorium–uranium distribution suggests the presence of local fluctuations with small amplitudes during the OAE3. Therefore, a more local behavior of the event is considered although the regional character is not neglected

The Logoualé Band: A large Archean crustal block in the Kenema-Man domain (Man-Leo rise, West African Craton) remobilized during Eburnean orogeny (2.05 Ga)

International audienceThe Archean domain of the Man Rise was strongly remobilized during Eburnean coincidentally with the genesis of the Baoulé-Mossi domain (Birimian). This remobilization has allowed the recycling of Leonian and Liberian formations to generate a large gneissic crust, represented by the Logoualé Band. Zircons dates by laser ablation (LA-ICP-MS) of two samples of biotite-bearing pink gneisses of the Logoualé Band yielded ages of 2709 ± 15 and 2804 ± 11 Ma, confirming the Archean age of the Logoualé Band formations. The Eburnean tectono-metamorphic event in the Logoualé Band has totally reset both U-Th-Pb chronometer with an average age at 2050 ± 16 Ma in recrystallized zones of monazites, and Sm-Nd chronometer of garnets with an age at 2053 ± 15 Ma. Non-recrystallized zones of monazites give an average age at 2712 ± 16 Ma. We propose that the Logoualé Band rocks were originally sediments deposited in some protocratonic rift-type basins. During Eburnean, these sediments were buried, underwent high-grade metamorphism and exhumed in a tectonic context dominated by transcurrent motion. The structural setting of banded iron formations (iron deposits), which are abundant in the Logoualé Band, would date back to the Eburnean