Rumaila Field Research Articles

Effect of Sodium Dodecyl Sulfate on the growth of sulfate -reducing bacteria isolated from water associated with oil production in the North Rumaila field, Basra Governorate – Iraq

Effect of Sodium Dodecyl Sulfate on the growth of sulfate -reducing bacteria isolated from water associated with oil production in the North Rumaila field, Basra Governorate – Iraq

Determining the sources and distribution of polycyclic aromatic hydrocarbons in the soil of different oil fields at Basrah governorate, Iraq

The object of the research is polycyclic aromatic hydrocarbons (PAHs). For the purpose of determining the source and distribution of PAHs, soil samples from the 11 oil fields in the Basrah governorate (Seba, Safwan, Majnoon, Ratawi, Bergezia, Qurna1, Qurna2, Shuaaba, South and North Rumaila, and al Zubair) were taken at a depth of 0 to 20 cm. According to their molecular weight, they were separated into two main groupings. The first group of compounds consisted of six compounds: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, and anthracene. These light (low molecular weight) compounds have two to three fused aromatic rings. The first group includes nine chemicals: floranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b), benzo(k), benzo(a), benzo(a), indeno(1,2,3,c,d), and benzo(g,h,i)perylene. These heavy (high molecular weight) compounds included four or more fused aromatic rings. The PAHs compounds ranged in value from the lowest (0.16 ng/g dry weight of benzo(a)anthracene at station West Quarna1) to the highest (680 ng/g dry weight of benzo(g,h,i)perylene that emerged at station North Rumail). The total concentration of PAHs ranged from 77.67 ng/g in South Rumaila Field while highest concentration is 2284.27 ng/g in North Rumail. The PAHs compound has low and high molecular weight, their ratio of LMW/HMW (low molecular weight/high molecular weight) and phenanthrene/anthracene, fluoranthene/pyrene indicated that the source of PAHs was pyrogenic only. The PAH diagnostic ratios and principal component analysis (PCA) indicated that PAHs in soils essentially originated from emissions and combustion. This study gave a baseline on the source and distribution of these compounds in oil fields at Basrah governorate and can be used as a baseline for coming study in the future.

Using mud gas while drilling analysis to predict reservoir fluid characteristics of the Zubair reservoir in north Rumaila field, southern Iraq

Using mud gas while drilling analysis to predict reservoir fluid characteristics of the Zubair reservoir in north Rumaila field, southern Iraq

Investigating the Behavior of Permeable and Impermeable Reservoirs in Southern of Iraq

The effect of hydraulic fracturing on the permeability and fluid flow of various Iraqi oil storage cores has been studied. Rumaila, Majnoon, and Zubair fields with different permeability were included in this study. Experiments were performed to determine the breaking pressure of the permeable core. Therefore, numerical and experimental results were compared to test the constant pressure on the impermeable core. Finite Volume Method (EbFVM) corresponding to the Dual Porosity Dual Permeability Model (DPDP) was used. A fractured reservoir in the Iraqi fields was studied for its single-phase fluid flow behavior. To represent the pressure distributions, ANSYS-CFX program was used. The comparisons between the fractured and non-fractured cores has been presented. In this paper, the pressure for permeable cores of Rumaila field has been determined and verified during the experimental and numerical simulation due to its lower fracture pressure. Hence, the required pressure has been determined for impermeable cores of Majnoon and Zubair fields due to the difficulties to measure such high pressure. The results show that the expected pressure to make a flow for the core belongs to the Majnoon field reaches to 1.724×107 Pa (2500 psi), while the expected pressure for the fluid to flow into the core belongs to the Zubair field reaches 1.379×108 Pa (20000 psi).

Bayesian averaging sensitivity analysis of reservoir heterogeneity and anisotropy of carbon dioxide assisted gravity drainage of a large clastic oil reservoir

Identifying the specific reservoir properties that influence oil production is an essential part of field development planning. Distinguishing the relative influence of variables and eliminating those that have no influence assists the design of enhanced oil recovery processes. The conventional approach to identify the most influential variables is the multiple linear regression (MLR) step-wise elimination. Bayesian averaging (BA), a stochastic method, offers a novel alternative approach by generating fifty models compared to each other to select the best one with of the most influential parameters based on the highest R2 and posterior probability with the lowest value of Bayesian information criterion (BIC). BA and MLR step-wise elimination are compared in the evaluation of a simulated immiscible carbon dioxide-assisted gravity drainage (CO2-AGD) system applied to the multi-layered, heterogeneous, upper sandstone oil reservoir of the South Rumaila field. A history-matched compositional simulation covering the nearly 57 years of prior production is used for sensitivity analysis of reservoir variables in relation to CO2-AGD implementation over 10 future years with 22 additional CO2 injection wells and 11 new production wells. Oil is displaced downwards towards the new horizontal production wells installed above the oil water contact. The influential variables evaluated are permeability (K), permeability anisotropy (Kv/Kh) and porosity (ɸ) considered separately across multiple heterogeneous reservoir layers. BA and step-wise elimination methods identify K as the most influential variable in all reservoir layers. Kv/Kh is moderately influential in the production layers and underlying water zone but not in injection or transition reservoir layers. ɸ in all reservoir layers has no influence on oil recovery from the CO2-AGD producing wells. More specifically, the BA-based influential parameters were determined after selecting the best model among the fifty generated models. The best model achieved that highest values of R2 of 0.848 and posterior probability of 0.234, and the lowest value of BIC of −149 with 12 identified influential geological parameters across the reservoir layers. Based on validation tests, varying K, Kv/Kh. and ɸ substantially across all reservoir layers confirms these findings and agrees more closely with the BA-derived reduced variable models than those generated by MLR step-wise elimination.

A novel approach to estimate rock strength parameters from multistage triaxial tests (the A-HAS method)

Rock strength parameters are vital to creating robust geomechanical models for wellbore stability, sand production, and hydraulic fracturing. Static rock strength parameters can be estimated from single stage triaxial tests (SST) or multistage triaxial tests (MST). Although SST tests are the most accurate way to estimate rock strength parameters, SST tests require at least four to five core plugs to estimate rock strength parameters. Thus, MST tests are used as an alternative method to estimate rock strength parameters from only one core plug to overcome the limitation of materials and save time and money. However, the currently used method to estimate rock strength parameters is the yield-based only method which can significantly underestimate rock strength (especially unconfined compressive strength (UCS)) and can hinder creating a robust geomechanical model. In this work, the authors proposed a novel method called the A-HAS method which is a correction to the yield-based method that is currently used. Using core plugs from three different zones (Nahr Umr shale, Zubair shale, and Zubair sandstone in the Rumaila field, Iraq), SST and MST tests were executed. Rock strength parameters were estimated based on SST tests for each zone (Base Case). Then, rock strength parameters were estimated based on four different methods; the currently used yield-based only method (Case 1) from MST, corrected maximum compressive strength (MCS) (Case 2 or the A-HAS method) from MST, and Cases 3 and 4 which are based on corrections from both SST and MST tests. The results have shown that regardless of the method used, coefficient of friction (μi) and internal friction angle (ɸ) were not significantly affected while UCS and cohesive strength (So) were highly affected. Comparing UCS and So results of the yield-based method (Case 1) and the A-HAS method (Case 2) to the Base Case, the A-HAS method has significantly outperformed the yield-based method in all three zones tested. The A-HAS method has resulted in errors of 4%, 3%, and 2% for Nahr Umr shale, Zubair shale, and Zubair sandstone, respectively while the yield-based method resulted in errors of 41%, 31%, 83% for Nahr Umr shale, Zubair shale, and Zubair sandstone, respectively. The error of the yield-based method is very significant and may hinder creating robust geomechanical models for wellbore stability, sand production, hydraulic fracturing, and many other applications. The authors recommend utilizing the novel A-HAS method to obtain rock strength parameters (especially UCS and So) from MST tests and not utilize the currently used yield-based method since the A-HAS has proven to be effective and produced better results in the three tested zones than the yield-based method. By using the A-HAS method, the limitations of the MST tests can be overcome and reliable results from MST tests can be achieved which will contribute to saving time, money, and material.

A new technique for forecasting pore pressure in two oil wells in North Rumaila field based on specific energy concept

Forecasting the pore or formation pressure is crucially significant in every well drilling operation to determine whether the pore pressure gradient is abnormal or subnormal. Abnormal pore pressure gradient means that the pore pressure gradient exceeds the gradient of the normal pressure, while when the opposite happens it means that the pore pressure is subnormal. Both cases required high care with special control of the mud weight to overcome the vital situation. Accurate pore pressure determination is rigorous in drilling engineering to plan for drilling hydrocarbon wells with appropriate mud program with less effort and cost. Precise forecasting of formation pore pressure prevents occurring various drilling hazards such as lost circulation, stuck pipe and well kick as a result of abnormal pore pressure. In the present work, a new technique was proposed to predict the pore or formation pressure from the specific energy. A new formula of specific energy was used involving the rock properties and the drilling parameters. The new specific energy formula is functioned later in Eaton’s equation to obtain a new suggested formula of pore pressure. There is a lack of researches in the literature that determine the real-time pore pressure without depending on well logs. Abnormal and subnormal pressure zones can be determined accordingly based on the fact that abnormal pressure intervals possess low effective stress and require less energy to drill than the intervals that have normal pressure at the same depth. The new proposed formula of pore pressure was tested in two oil wells in North Rumaila field (N14 and N15) in Basrah province south of Iraq. The obtained pore pressure from the new technique based on the suggested specific energy formula that involves the physical properties of the rock being excavated and the drill bit is compared with the actual (measured) pore pressure derived from other wells in North Rumaila field using measurements while drilling logs, drill stem test and real formation test. There was a good rapprochement between the predicted and the measured pore pressure. The present approach depends mainly on the value of the slope (m) which is determined and varied from one place to another. The new method could provide an alternative method for estimating the pore pressure especially for wells being planned to be drilled where the actual pore pressure is unknown and there is shortage in well logs and formation tests, where most of the previous articles in the literature depend mainly on well logs of adjacent wells in predicting the pore pressure of a specific well. The findings of this study can help for better understanding the prediction of formation or pore pressure that helps to choose the appropriate mud weight to control the well without collapsing and preventing well kick that might occur.

Study the Effect of Corrosion on the Pipes of Oil Well Production

Corrosion costs of the oil industry are billions of dollars in a year. Corrosion affects every aspect ofexploration and production of oil, from offshore rigs to casing and transporting the crude oil torefinery or exporting terminal. This study aims to investigate the effect of sulfur content on thecorrosion of carbon steel and composite material (polyester/fiberglass) pipes used in wellproduction. .In the present work three specimens of pipes from (Al – Nasiriyah oil field, Al – Daura refinery, andcomposite material) are prepared in the center of the training and workshop in university oftechnology with (3, and 5 mm) thickness and (30 mm) diameter which immersed in different typesof Iraqi crude oil field (East – Baghdad, Al – Nasiriyah, and Al – Rumaila field) in different times (0,14, 28, 42, and 56 day). Physical properties (viscosity, density, API grade, specific gravity (sp.gr),sulfur %, sediment %, and water %) of three types of Iraqi crude oil are tested in lab of petroleumtechnology department. Also study specimens of pipes by microscope to knowing the effect ofsulfur % on these specimens. .The results showed that when increasing duration of immersed pipes and sulfur content in crude oilincreased the rate of corrosion, and the composite material pipe gives the best result compared withthe other two specimens pipes used because they didn’t influenced by corrosion when immersed inIraqi crude oil. Also, it was noted that the diffusion coefficient decreased in composite pipecompared with the other pipes.

Pore-Structure Characterization of a Complex Carbonate Reservoir in South Iraq Using Advanced Interpretation of NMR Logs

The Rumaila Field is in southeast Iraq and contains multiple reservoir intervals, including the Upper Cretaceous Mishrif carbonate reservoir, one of the major reservoirs in the world, that has been producing for more than 50 years. One of the key challenges in the Mishrif is to characterize the pore-structure distinction between primary and secondary porosity. The secondary porosity in the form of large pores, if present, dominates the petrophysical properties, especially permeability. Advanced logs, e.g., nuclear magnetic resonance (NMR) and image logs, can be used to understand the variations in pore structure, both qualitatively and quantitatively. In this paper, we focused primarily on four new wells with very comprehensive logging and coring programs. NMR logs were acquired using different tools and pulse sequences. This resulted in uncertainty in porosity and T2 distributions and, consequently, complications in the NMR interpretation. We observed two key issues: porosity deficit due to lack of polarization and T2 distribution truncation due to the low number of echoes. We used a single pore model to reproduce the NMR response in different pore sizes and fluid types for different pulse sequences. The results showed that the NMR response, especially in water-filled (water-based-mud filtrate) large pores, is sensitive to polarization time, echo spacing, and tool gradient strength. NMR log data confirmed the modeling results. We recommended an optimum pulse sequence and tool characteristics to fully capture the heterogeneous rock and fluid system in this carbonate reservoir. NMR logs, when available, were the primary tools to identify the large pores. We present a consistent workflow for NMR log analysis that was developed to identify and quantify large pores and extended to all wells in the field. We used advanced NMR interpretation techniques, e.g., factor analysis (NMR FA) (Jain et al., 2013), in a series of oil wells drilled with water-based mud. Using factor analysis, we identified a cutoff value of 847 ms for large pore volumes. In this manuscript, we also present an integration of laboratory measurements, e.g., NMR, mercury intrusion capillary pressure (MICP) data, whole-core CT scanning, and thin-section analysis, in our interpretation workflow. We also compared the large pore volume from image logs with NMR logs and other laboratory data and observed very consistent results. All the available information was integrated to build an “NMR-based” petrophysical model for porosity, rock type, permeability, and saturation determination. The NMR-based model was very comparable with the classic flow zone indicator (FZI) rock typing. The results of this study were used to modify the NMR acquisition program in the field and to build a petrophysical model based on only NMR and image log measurements for carbonate reservoirs. In this paper, we will discuss NMR modeling and corresponding log data from various wells to confirm the results. Furthermore, we will present a novel interpretation workflow integrating laboratory measurements and log data, which led to the modification of the NMR acquisition program in the field and the creation of a data-driven petrophysical model based on only NMR and image log measurements for carbonate reservoirs.

OPTIMIZE THE PERFORMANCE OF ELECTRICAL EQUIPMENT IN GAS SEPARATION STATIONS (DEGASSING STATION DS ) AND ELECTRICAL SUBMERSIBLE PUMPS OF OIL EQUIPMENT FOR OIL RUMAILA FIELD

Annotation: There are various types of electrical equipment used in the extraction of oil at the Rumaila field, with an average voltage of 11 kV and a low voltage of 0.4 kV. The most common elements in this class are transformers and reactors, engines and gas discharge lamps. All of this equipment consumes reactive power and reduces the value of the power factor. (Power factor is the ratio of kW to kVA). The closer the power factor to the maximum possible value of 1, the greater the benefit for the consumer and supplier. In case of low power factor, the current will be increased, and this high current will lead to (large line losses, an increase in the nominal total power of kVA and overhaul dimensions of electrical equipment, deterioration in voltage regulation process and an increase in voltage drop, a decrease in efficiency).Power factor improvement allows the use of smaller transformers, switchgear and cables, etc. as well as reducing power losses and voltage drop in an installation. Improving the power factor of an installation requires a bank of capacitors which acts as a source of reactive energy. These arrangements provide reactive energy compensation. In Rumila, An improvement of the power factor of an installation presents several technical and economic advantages, notably in the reduction of electricity bills, we save (685.854.007 Iraqi Dinar= 550.000 $) for one month . All this work takes 6 to 12 month.

Technology Focus: Seismic

Technology Focus Last year saw continued contraction in the seismic data-acquisition industry. This included both onshore and offshore operations. Most notably, WesternGeco exited land and marine data acquisition. (In the case of marine, WesternGeco sold all of its vessels, facilities, and technologies to Shearwater GeoServices.) Ironically, it was just 1 year ago when I discussed in this column the new and exciting acquisition-related advances in the industry that had been developed for the purpose of better data sampling. With this drop in acquisition business, it is not surprising that there were fewer seismic data-acquisition papers published in SPE proceedings. Nevertheless, several excellent SPE papers covered important acquisition and processing topics. One of the papers deals with the current state of the art for addressing marine challenges. This is described with a 3D case history from the Gulf of Thailand. Another paper deals with leading-edge techniques that were used in a recent onshore 3D survey in Abu Dhabi. And a third paper showcases the application of a relatively new technology, distributed acoustic sensing (DAS). DAS is rapidly finding a home in vertical-seismic-profile surveys and in unconventional programs. Indeed, this third paper deals with a DAS study performed in the Marcellus Shale. Offsetting the drop in the number of acquisition papers was a proportionate increase in the number of SPE papers that covered other important seismic topics. These included inversion and reservoir characterization, 4D interpretation, seismic for carbonate plays, and machine learning. (Similar to what is happening in other industries, machine learning is receiving tremendous attention now in the seismic world.) Though industry fluctuations may affect our areas of specialty, there will always be room for improvement driven by innovation. Recommended additional reading at OnePetro: www.onepetro.org. SPE 189888 Seismic Attributes Application for the Distributed Acoustic Sensing Data for the Marcellus Shale: New Insights to Cross-Stage Flow Communication by Payam Kavousi Ghahfarokhi, West Virginia University, et al. SPE 192948 How Broadband, High-Density, Full-Azimuth, and Point-Source Point-Receiver Acquisition Improves Seismic Interpretation in Onshore Abu Dhabi by Sheikha Al-Naqbi, ADNOC Onshore, et al. SPE 192956 Comparing Seismic Inversion Methods on a Carbonate Reservoir: A Case Study From the Mishrif Reservoir, Rumaila Field, Iraq by Olabode Joseph Olatoke, BP, et al. SPE 192927 Effect of Seismic Acquisition and Processing Techniques in Challenging Subsurface Imaging, Block G11/48, Gulf of Thailand by Phansakorn Kaewprain, Mubadala

OPTIMAL OPERATION OF ELECTRICAL POWER GENERATORS FOR OIL WELLS OPERATED BY ARTIFICIAL LIFTING AT RUMILA FIELD

Numerous oil wells within Rumaila field contain Electrical Submersible Pumps (ESPs). ESPs are utilised to maximise the oil production from existing wells by providing artificial lift where pressure is low, which helps maintain oil production levels. The number of ESPs installed throughout the Rumaila. Field is growing consistently to sustain oil field production. Due to the remote locations for each of the ESPs the current strategy is to supply power to ESPs using individual diesel engine generators located at each remote ESP well site. This is an inefficient design, as individual diesel engines are resource intensive due to maintenance and frequent diesel filling. The generators are also a source of significant unreliability causing ESP shutdowns/trips resulting in extended downtime. Given the above a Pre-FEED has been carried out considering supplying ESPs using OHTL’s supplying electrical power from EPP to ESPs in Area C. by uses parallel operation of diesel Generators , we could to constrict 124 from 184 and use 60 only ,by this we get high economic gain and technique, in additional that environmental protection by decreasing pollution.

Stochastic inversion by trace matching for carbonate reservoir property prediction: A Mishrif Reservoir case study

Estimation of reservoir properties and facies from seismic data is a well-established technique, and there are numerous methods in common usage. Our 1D stochastic inversion process (ODiSI), based on matching large numbers of pseudowells to color-inverted angle stacks, produces good estimations of reservoir properties, facies probabilities, and associated uncertainties. Historically, ODiSI has only been applied to siliciclastic reservoir intervals. However, the technique is equally suited to carbonate reservoirs, and ODiSI gives good results for the Mishrif Reservoir interval in the Rumaila Field in Iraq. Of course, a thorough awareness of the quality of all input well data and detailed validation of the parameters input to the inversion process is crucial to understanding the accuracy of the results.

Real-time lost circulation estimation and mitigation

Lost circulation is a challenging problem particularly in the Dammam formation of the Rumaila field, Iraq. Drilling engineers are challenged to select the optimum value for key drilling parameters such as equivalent circulation density (ECD), yield point (Yp), mud weight (MW), weight on bit (WOB), rate of penetration (ROP) and revelation per minute (RPM) to mitigate mud losses in this formation. Many of these drilling parameters are inter-related and the overall impact of changing key parameters requires extensive drilling experience or study.A multi-regression analysis was performed on mud loss event data for more than 300 wells drilled in the Dammam formation. From this analysis, a model was developed to predict the total mud losses. Mud loss was found to be significantly affected by MW, ECD, and ROP. Models for these key parameters were also developed from the multi-regression analysis. The models were confirmed with additional well data from new wells drilled in the field. The models developed in this work provides a method for setting predicted mud losses, then limiting the operational drilling parameters to mitigate such losses in the future wells in fields with similar lithology.Proactive approaches are made prior to entering the Dammam formation to prevent or mitigate the occurrence of the lost circulation. Key drilling parameters are estimated to use during drilling through this formation. In case preventive measures didn’t work, corrective actions are determined for each type of mud losses to provide effective remedies, minimize non-productive time, and reduce cost. The best lost circulation strategy to the Dammam formation is concluded and summarized depending on a comprehensive statistical work, the most important courses of the international oil companies, technical papers, textbooks, and economic evaluation to determine the successful remedies for each type of losses. These treatments are classified by relying on the mud losses classifications to avoid unwanted consequences due to inappropriate actions.

Overburden stress and pore pressure prediction for the North Rumaila oilfield, Iraq

The aim of this study is to give an estimation of the pore pressure in all formations starting from surface to the main reservoir (Zubair Formation) in North Rumaila oilfield. Pore pressure estimation is fundamental in minimizing the nonproductive time (NPT) caused by wellbore instability or mud losses. Two methods were used to predict pore pressure: first, direct measurements of by RFT tool where almost all measurements indicated low pore pressure within reservoirs intervals (Zubair, Nahr Umr and Mishrif Formations) as a result of hydrocarbon production. Second, the indirect prediction, this technique relied on the disparity of the petrophysical characteristics of normally and abnormally compacted formations determined by the compressional transit time data (∆t). This method showed that most of the formations in Rumaila field are equal or less than the normal compaction trend line (NCTL) except the Shale layers in Tanuma, Ahmadi and Zubair Formations as these layers exhibit low permeability and subjected to under-compaction which occurs in rapidly subsiding basins.

Development of Ratawi Oil Field, Southern Iraq

Ratawi Field is a promising hydrocarbon bearing structure conforming several reservoirs, and lies northwest of the Basrah city and west of Northern Rumaila Field. Kinetic Analysis referred to that the type of Fold of Ratawi Structure similar to the types which are associated with Salt Structure activity.Geophysical Interpretation referred to the presence of Salt Structure beneath Ratawi Structure. The Isopach Maps shows that the crest thickness is less than the limbs, this characteristics is always due to those of salt structures beneath Ratawi field. Both of Tectonic Movement and Salt Structure play a great role in forming and development of Ratawi Structure.

Practical Strategies and Engineered Solutions to Minimize the Impact of Lost Circulation Problem

Lost circulation is a complicated problem to be banned or combatted during the drilling operations. Mud losses remedies are extensively used to stop or mitigate losses using remedial methods or to prevent mud losses using proactive measures. Lost circulation presents a lot of big challenges during drilling. To address these problems, a number of methods/techniques have evolved over the years. The Rumaila field in Iraq is one of the largest oilfields in the world. Wells drilled in this field are highly susceptible to lost circulation problems when drilling through the Hartha formation. Lost circulation events range from seepage losses to complete loss of the borehole and are a critical issue in field development. This paper describes a study of the lost circulation events for more than 300 wells drilled in the Rumaila field. Lost circulation events were extracted from daily drilling reports, final drilling reports, and technical reports. Key drilling parameters (e.g. ROP, SPM, RPM, WOB, bit type) and mud properties (e.g. mud weight, yield point, gel strength) at the time of each event were recorded along with the lost circulation remedies attempted, and the outcome of those remedies. These data have been analyzed to determine the best ranges of the key drilling parameters that have the greatest chance of mitigating lost circulation in the Hartha formation. Practical field information from the Rumaila field and range of sources have been reviewed and summarized to develop an integrated methodology and flowchart for handling lost circulation events in this formation. In a related development, this paper will be extended work along with previous comprehensive statistical study and sensitivity analysis models about the Hartha formation to obtain the best field procedures for avoiding or minimizing lost circulation events in the Hartha formation. Proactive approaches have been made prior entering the Hartha formation to prevent or mitigate the occurrence of lost circulation. A unique statistical work, primitive mechanisms, typical drilling fluid properties and recommended operational drilling parameters have been evaluated to use during drilling the Hartha formation. In addition, corrective actions have been determined for each kind of the mud losses to provide effective remedies, minimize non-productive time, and reduce cost. Lost circulation strategy to the Hartha formation has been summarized depending on statistical work and economic analysis evaluation to determine the most successful remedies for each type of the losses. These treatments are classified by relying on the mud losses classifications in order to avoid unwanted consequences due to inappropriate actions. This study provides a typical compilation of information regarding traditional approaches and the latest approaches to lost circulation control. In addition, the work attempts to provide useful guidelines or references for both situations in terms preventive measures, remedial methods, and analytical economic study.

Limiting Key Drilling Parameters to Avoid or Mitigate Mud Losses in the Hartha Formation, Rumaila Field, Iraq

Wells drilled in Rumaila field are highly susceptible to lost circulation problems when drilling through the Hartha formation. This paper presents an extended statistical work and sensitivity analysis models of lost circulation events in more than 100 wells drilled in Rumaila field. Lost circulation data are extracted from daily drilling reports, final reports, and technical reports. The volume loss model is conducted to predict the mud losses in the Hartha formation. Observations that are made from the volume loss model are ECD, MW, and Yp have a significant impact on lost circulation respectively; however, SPM, RPM, and ROP have a minor effect on the mud losses. Equivalent circulation density model is obtained to estimate ECD in the Hartha zone, and from this model can be deduced that MW, ROP, and Q have a significant impact on ECD respectively; nevertheless, RPM and Yp have a minor impact on the ECD. The rate of penetration model is made to estimate ROP in the Hatha zone. It is concluded that WOB, RPM, and SPM have a significant impact on the ROP respectively. Due to the lack of published studies for the Hartha formation, this work can serve as a practical resource for drilling through this formation.

Reservoir-scale sequence stratigraphy of Mishrif carbonates and implication to water injection strategy North Rumaila field case

The Late-Cenomanian–Early-Turronian Mishrif multi-carbonates in the North-Rumaila oil field has undergone into reservoir-scale high-resolution sequence stratigraphic investigation. Five-carbonate sequences (M4, M5, M6, M7, and M8) are established, comprised by (fifth-order high-frequency lithofacies cycles). The chrono-surfaces (CS5, CS6, and CS7) have screened a particular construction of Rudistid-bioaccumulated-bank/shoal buildups across the North Rumaila field. The CS6 marker has clarified two main evolutionary stages of the bank structure. The first case indicates the bank buildup crossed by the CS6 marker, whereas the second case signifies a stage the marker terminating the bank by well-developed lagoonal facies. The recognized single high-frequency lithofacies cycle expresses a well developed shallowing-upward progression of mud-to-grain-dominated bioclastic wackestone/packstone facies as (non/semi-TMF characters) to coated grain (bioclastic)/peloidal grainstone facies as TMF grade. Four-chronostratigraphically based reservoir units are structured: reservoir cycle sets (M8a), (M7a), (M6a) and cycle set (M5b). Two chronostratigraphic cross sections based on CS6-flattening surface represent south-north alignment of the studied wells illustrates the bank buildup pre-to-post CS6 time, defining a new approach of the vertical stacking/lateral continuity pattern of the depositional cycles. This new approach clarifies a new Mishrif reservoir architecture in the field, highly foremost, and controls the reservoir dynamics. Accordingly, four sectional Rudist bank/shoal/lagoonal buildups are introduced, covered 25 NR wells (12 representative + 13 involved). For safe production from Mishrif carbonates, a proposed sequence stratigraphic philosophy with water injection consideration is submitted.

Reservoir flow unit identification of the Mishrif formation in North Rumaila Field

North Rumaila Oil Field is located about 54 km to the west of the Basra in southern Iraq. The Mishrif Formation in North Rumaila is one of the most important reservoirs in southern Iraq. Identifying and characterizing petrophysical flow units are the key to understanding and improving reservoir description, exploitation, and production and predicting the performance of carbonate reservoirs to represent them as combinations of different flow units, each with uniform pore throat size distribution and similar performance. The present work is a reservoir unit identification of the Mishrif Formation in North Rumaila Field. It is based on 14 wells, nine of which are from North Rumaila Field, three wells from West Qurna Field, and two wells form South Rumaila Field. In this study, the main reservoir units of Mishrif Formation are subdivided into subunits depending on the similarity of the log curves, water saturation–porosity–depth relationship, capillary pressure data, porosity–permeability cross plots (R35), flow zone indictor approach, and computer-processed interpretation. Unit MI, which is equal to unit MA, was subdivided into two secondary reservoir units (MI.1 and MI.2), and unit MII, which is equal to unit MB1, was subdivided into four secondary reservoir units (MII.1, MII.2, MII.3, and MII.4), while unit MIII, equal to unit MB2, was considered as one flow unit. As a result, we conclude that of the subunits, MII.4 is considered the most important reservoir in the field, subunits MI.1 and MII.2 may be classified as good reservoirs, whereas subunits MI.2 and MII.1 are of moderate reservoir characteristics. On the other hand, subunit MII.3 and unit MIII may be classified as intermediate–poor reservoir characteristics.