|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
This paper describes the first application of clay-free IEFs in the Norwegian continental shelf (NCS), with an emphasis on an impressively low and consistent ECD contribution. This year has been a great year for me; I was able to play more rounds of golf than expected! I was also successful in sealing a few research collaboration agreements within the oil and gas industry.
You have access to this full article to experience the outstanding content available to SPE members and JPT subscribers. To ensure continued access to JPT's content, please Sign In, JOIN SPE, or Subscribe to JPT While drilling in deepwater Gulf of Mexico, a topdrive failure forced the shutdown of all drilling operations for the rig operator and lasted for 114 hours (almost 5 days). At the time of the failure, the equivalent static density (ESD) was 11.36 ppg and the equivalent circulating density (ECD) was 11.5 ppg. The rate of penetration (ROP) was 100 ft/hr. It was recommended that there be no utilization of the pumps while drilling was stopped, to reduce the chance of packing off the annulus with cuttings until the rotating and reciprocating could continue.
Roostaei, Morteza (RGL Reservoir Management Inc.) | Hosseini, Seyed Abolhassan (University of Alberta and RGL Reservoir Management Inc.) | Soroush, Mohammad (University of Alberta and RGL Reservoir Management Inc.) | Velayati, Arian (University of Alberta) | Alkouh, Ahmad (College of Technical Studies) | Mahmoudi, Mahdi (RGL Reservoir Management Inc.) | Ghalambor, Ali (Oil Center Research International) | Fattahpour, Vahidoddin (RGL Reservoir Management Inc.)
Summary Sieve analysis, sedimentation, and laser diffraction (LD) have been the methods of choice in determining particle-size distribution (PSD) for sand control design. However, these methods do not provide any information regarding the particle shape. In this study, we introduce the application of dynamic image analysis (DIA) to characterize particle sizes and shape descriptors of sandbearing formations. Different methods were compared in the estimation of PSD and fines content, which are the primary factors important in sand-control design. Through minimizing the sampling and measurement errors, the deviation between different PSD measurement techniques was attributed solely to the shape of the particles and the amount of fine fraction. For fines-content measurement, the values obtained through Feret min parameter values (the minimum size of a particle along all directions) calculated by DIA and sieving measurement are comparable within a 5% confidence band. The deviation between the results of different methods becomes more significant by increasing fines content. The fines and clay content show higher values when measured by any wet analysis. LD also tends to overestimate the fines fraction and underestimate silt/sand fraction compared with other dry techniques. By comparing the deviation of the DIA and sieving at standard mesh sizes, an algorithm has been developed that chooses the equivalent sphere sizes of DIA with minimum deviation from sieving. This study performs several measurements on formation sands to illustrate the real advantage of the new methods over traditional measurement techniques. Furthermore, particle-shape descriptors were used to explain the deviation between the results of different PSD measurement methods. Introduction One of the main factors in classifying the components of soil is the investigation of the size distribution of the particles. PSD is generally being used for soil classification and some hydraulic properties including soil's permeability, porosity, consolidation, and shearand volume-change behavior (Campbell and Shiozawa 1992). Furthermore, depositional history of transported soil and development of in-situ soils are also being evaluated by PSD. Thus, PSD provides valuable information in engineering and other fields such as environmental geoscience, sedimentology, and pedology. Studies confirmed that there are major problems associated with sedimentation methods including their time-consuming procedure, need for a fairly large number of samples (20 g), and dependency of the results on laboratory equipment, specific technique, or operation (Percival and Lindsay 1996).
Mud losses are frequently observed when drilling in depleted formations. This is because of the decrease in the minimum in-situ stress during depletion. As a result of this decrease, the lost-circulation pressure—or fracture gradient (FG)—decreases, and the operational mud-weight window shrinks. Losses in such formations are often observed when drilling through sand/shale sequences. Preventing and curing losses requires a sound understanding of loss mechanisms. In this study, we investigate several mechanisms that might be responsible for the elevated risk of mud losses in differentially depleted sand/shale sequences. Numerical models of synthetic cases representative of lost-circulation scenarios in a high-pressure/high-temperature (HP/HT) field in the North Sea, under normal faulting conditions, are set up using the finite-element method. The simulations reveal that shear displacement at the horizontal sand/shale interfaces is unlikely to cause losses. On the other hand, shear displacement and losses might be induced at high-angle sand/shale interfaces, such as those found near faults. In addition, faults introduce an extra complexity to the stress distribution and stress-path coefficients. Stress anisotropy near faults might increase during depletion, making both lost-circulation issues and borehole-stability problems worse. The zone most prone to lost circulation in a faulted formation is located in depleted sand adjacent to the fault. The loss mechanism here is because of drilling-induced fractures (DIFs). In addition, depletion itself might induce fractures in shale adjacent to the depleted sand and located across the fault from it. Such fractures might then serve as escape paths for the drilling fluid during infill drilling. The loss mechanism here is caused by pre-existing, depletion-induced fractures. These findings are in agreement with field observations. A noncircular (elliptic or irregular) borehole cross section is found to reduce the fracture-initiation pressure (FIP). An irregular borehole cross section is, thus, another possible mechanism behind irregular loss patterns observed in depleted fields. The results from the study are important for establishing best practices when drilling in depleted formations.
Quantification of fluid losses at the topside is beneficial for early kick-loss detection and automation of the drilling operation. A model-based estimator is a useful tool for this purpose. The real-time estimation of the amount of fluid losses with the cuttings removal could significantly help in this regard, especially for kick detection and automation. However, to the authors’ knowledge, there is no published literature on such attempts. Therefore, a simple dynamic mathematical model of the complete closed-loop oil-well drilling system is developed in this study for estimation of the fluid losses during the removal of drill cuttings at the topside, as well as for monitoring the flow of return fluid during drilling. Furthermore, this model could provide information about the topside fluid-flow rates and fluid losses to other monitoring systems, such as kick- and loss-detection systems and automation systems. The model is used to estimate both the mud-pit level and the fluid losses during the removal of the drill cuttings through the solids-removal equipment. The model-order reduction of the flowline model using orthogonal collocation allows the model to be used in real-time estimations and/or with control systems. It is simple, easy to implement, and, more importantly, shows the necessary dynamic behavior of both the bottomside and topside of a drilling operation simultaneously. The topside model can be used together with bottomside models of varying complexity to estimate both the bottomhole pressure and the fluid losses through the solids-removal system.
Drill-conductor-jetting technology is a high-efficiency, good-adaptability, and low-cost technology that has been widely applied in deepwater drilling. However, a reaming effect will be produced easily because of jet breaking and bit rotation during the jetting process, and the critical displacement would be notably affected. Also, it will experience a relatively short soaking time after installation because of the requirements of drilling timeliness, which is an important factor on the bearing safety of a conductor. Therefore, it is meaningful to study the influencing factors of construction conditions and establish a model for evaluating the value of critical displacement. In this study, field experiments on critical displacement for simulating the deepwater-drilling conditions were conducted. By analyzing the drilling hydraulic factors, the effects of soil-stress-recovery time, and the injection rate of pipe, the influence laws of different factors were obtained. The results suggest that the critical displacement increases linearly as the circulation rate of the drilling fluid increases, decreases exponentially with the increase of soil-stress-recovery time, and decreases linearly with the increase of injection rate. One model for estimating the critical displacement using experimental data and the least-squares method was proposed. The predictions showed good agreement with experimental data within suitable ranges of models. This work is expected to provide the basis for predicting conductor stability and wellhead-bearing settlement.