Transient Thermal Effects in Sedimentary Basins with Normal Faults and Magmatic Sill Intrusions—A Sensitivity Study

Abstract

Magmatic intrusions affect the basin temperature in their vicinity. Faulting and physical properties of the basin may influence the magnitudes of their thermal effects and the potential source rock maturation. We present results from a sensitivity study of the most important factors affecting the thermal history in structurally complex sedimentary basins with magmatic sill intrusions. These factors are related to faulting, physical properties, and restoration methods: (1) fault displacement, (2) time span of faulting and deposition, (3) fault angle, (4) thermal conductivity and specific heat capacity, (5) basal heat flow and (6) restoration method. All modeling is performed on the same constructed clastic sedimentary profile containing one normal listric fault with one faulting event. Sills are modeled to intrude into either side of the fault zone with a temperature of 1000 • C. The results show that transient thermal effects may last up to several million years after fault slip. Thermal differences up to 40 • C could occur for sills intruding at time of fault slip, to sills intruding 10 million years later. We have shown that omitting the transient thermal effects of structural development in basins with magmatic intrusions may lead to over-or underestimation of the thermal effects of magmatic intrusions and ultimately the estimated maturation.

A Summary of “Future Advances in Basin Modeling: Suggestions from Current Observations, Analyses and Simulations”

“…Sydnes et al [9] report the results of a sensitivity study of the impact of sills on temperature and maturation when attendant faulting is taken into account. They show that omitting structural changes related to magmatic intrusion may lead to over-or underestimation of the thermal effects of magmatic intrusions and the timing of maturation.…”

The Influence of Magmatic Intrusions on Diagenetic Processes and Stress Accumulation

“…The sills are relatively thin and the distances between the sills are unknown in the study by Haile et al [14], which could explain the contrasting conclusions of their study and ours. The magmatic sill thickness, distance from sills, and clusters of sills are pointed out in several studies to have significant importance on the thermal effect of magmatic intrusions (e.g., [3,5,6,[9][10][11]). Our study shows that thermal effects will also affect diagenetic transformations (i.e., Figure 5).…”

“…This could also to some degree explain the contrasting conclusions. The host rock pre-intrusion temperature is identified to be crucial for the thermal effect of magmatic intrusions (e.g., [5,8,11]), and ultimately the effect of magmatic intrusions on diagenetic processes. Factors such as fault displacement, time span of faulting and sediment deposition, fault angle, rock of 28 thermal conductivity and specific heat capacity, basal heat flow, and restoration method used to simulate the fault movement through time, are all factors that influence the host rock pre-intrusion temperatures.…”

“…Factors such as fault displacement, time span of faulting and sediment deposition, fault angle, rock of 28 thermal conductivity and specific heat capacity, basal heat flow, and restoration method used to simulate the fault movement through time, are all factors that influence the host rock pre-intrusion temperatures. For a specific, detailed area study, all these factors are crucial and require thorough assessment [11].…”

“…Therefore, when emplaced into sedimentary basins, they may influence all parts of the petroleum system [1]. Several studies have shown how such intrusions influence the temperatures and hydrocarbon maturation in sedimentary basins (e.g., [2][3][4][5][6][7][8][9][10][11]). Other studies focus on the stress induced by the sills on the host rocks as they intrude (e.g., [12,13]).…”