Tight Condensate Research Articles

A transient production prediction method for tight condensate gas wells with multiphase flow

Considering the phase behaviors in condensate gas reservoirs and the oil-gas two-phase linear flow and boundary-dominated flow in the reservoir, a method for predicting the relationship between oil saturation and pressure in the full-path of tight condensate gas well is proposed, and a model for predicting the transient production from tight condensate gas wells with multiphase flow is established. The research indicates that the relationship curve between condensate oil saturation and pressure is crucial for calculating the pseudo-pressure. In the early stage of production or in areas far from the wellbore with high reservoir pressure, the condensate oil saturation can be calculated using early-stage production dynamic data through material balance models. In the late stage of production or in areas close to the wellbore with low reservoir pressure, the condensate oil saturation can be calculated using the data of constant composition expansion test. In the middle stages of production or when reservoir pressure is at an intermediate level, the data obtained from the previous two stages can be interpolated to form a complete full-path relationship curve between oil saturation and pressure. Through simulation and field application, the new method is verified to be reliable and practical. It can be applied for prediction of middle-stage and late-stage production of tight condensate gas wells and assessment of single-well recoverable reserves.

Influence of Compositional Gradient Effect on Tight Condensate Gas Reservoir Development

Condensate gas is a transition fluid between oil and gas, which is sensitive to the reservoir temperature and pressure. In condensate gas reservoir, especially in the moderate-giant one, fluid composition often varies with depth. This phenomenon has important influences on development. Anisothermal compositional gradient theory is used to analyze the main factors influencing the compositional gradient distribution to understand the basic regularities of the compositional variation with depth. Geothermal gradient, fluid composition, reservoir temperature, and reservoir pressure will affect the compositional gradient, of which geothermal gradient has the most direct and obvious influence. Furthermore, fluid model with compositional gradient was built in a tight condensate gas reservoir of the Middle East, and the influence of compositional gradient on dynamic performance is evaluated. The results show that the compositional gradient has a significant influence on the original gas in place, development strategy, central processing facilities, and so on. Therefore, compositional gradient requires more attention while exploiting moderate-giant condensate gas reservoirs in order to achieve more economical benefits.

A Comparison between Klinkenberg and Maxwell-Stefan Formulations to Model Tight Condensate Formations

Summary Cyclic solvent (gas) injection is an efficient recovery method for condensate reservoirs. However, in tight, unconventional formations, the added complexity of low permeability results in more physics at play, beyond the widely used Darcy model for conventional reservoirs. In this work, a rigorous mass transfer model is implemented considering the real gas version of the Maxwell-Stefan formulation to evaluate cyclic injection schemes in tight condensate reservoirs. This model is then compared to the more widespread used Klinkenberg formulation, which does not include molecular diffusion. An evaluation is performed to check if a simplified formulation can be used to provide reasonable results in modeling production and enhanced recovery in tight condensate formations. Verification of the implemented equations is performed using experiments (Maxwell-Stefan model) and a commercial reservoir simulator (Klinkenberg model). Furthermore, the cell length used for the numerical studies is selected based on a sensitivity study to evaluate how numerical dispersion impacts recovery factor and liquid saturation for different cell sizes. By comparing the Klinkenberg model with different tangential momentum accommodation coefficient (TMAC) values to the Maxwell-Stefan model during primary production, it is possible to select a value of TMAC that can match closely the recovery values of lighter components when using the Maxwell-Stefan equations. However, for heavier hydrocarbon fractions, difference in recovery is more accentuated owing to increased molecule size (more molecular friction). This results in differences in condensate yield during primary production that may be relevant in a field scale. In the cyclic injection scheme, the importance of accounting for frictional effects between molecules is demonstrated using the Maxwell-Stefan formulation. In this case, molecular diffusion fluxes are influenced by high composition gradients. This results in differences between the Maxwell-Stefan and Klinkenberg models in terms of gas stored and hydrocarbon produced during cyclic injection simulations. Furthermore, a sensitivity study on operational parameters in the cyclic injection stage demonstrated that increasing the length of production cycles may be more beneficial than increasing the length of injection or soaking cycles. For the simulations in this study, the gas is injected above the dewpoint and pressure diffusivity is at least one order of magnitude higher than the other physics present in the process. Therefore, increasing the length of production cycles allows for recovery of heavier hydrocarbon fractions that remain in the gas phase. In this work, it is demonstrated that using a rigorous mass transfer formulation, such as the Maxwell-Stefan equations, can provide more information on a per component basis when evaluating cyclic injection schemes in tight condensate reservoirs.

Preparation and characterization of super hydrophobic/oleophobic material and its application in releasing liquid locking in tight condensate gas reservoirs

In this paper, a super hydrophobic/oleophobic material CS-1 with super hydrophobic/oleophobic properties was successfully prepared with nano silica as the main raw material and 1H, 1H, 2H, 2H-perfluorooctyl trichlorosilane as modifier. The structures of synthesized product were characterized by the infrared spectroscopy (FTIR). The contact angle of super hydrophobic/oleophobic material CS-1 was measured by contact angle measuring instrument, and its hydrophobic/oleophobic properties were analyzed systematically. The micro-morphology of super hydrophobic/oleophobic material CS-1 was determined by scanning electron microscope. The results of wetting properties show that the maximum water phase contact angle of hydrophobic/oleophobic material CS-1 is 159.58° and the maximum oil phase contact angle is 135.63°. Based on triple action of constructing micro-nanostructure on rock surface, reducing gas-water surface tension and oil-water interfacial tension, the optimized formula of the unlocking agent 1.5 wt% super hydrophobic/oleophobic material CS-1 + 0.06 wt% NFS surfactant +0.09 wt% C3 Gemini surfactant was screened by single factor method. Finally, the performance of unlocking agent is comprehensively evaluated by surface energy spectrometer, laser particle size analyzer, automatic contact angle tester and core unlocking equipment. The results show that the water phase contact angles of the core treated with the unlocking agent are greater than 150° and the oil phase contact angles are greater than 130° in acidic, alkaline and high temperature environments. The maximum recovery rate of water locking damage gas measurement permeability is 91.1%, and the maximum recovery rate of oil locking damage gas measurement permeability is 67.4%. It shows that the unlocking agent can effectively improve the gas logging permeability of the core and change the wettability of the core surface, so as to relieve the liquid locking of the condensate gas reservoir. It has a good application prospect in the middle and late stage of condensate gas reservoir development.

Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs

The development of tight condensate gas reservoirs faces complex formation damage mechanisms, seepage characteristics and hydrocarbon phase changes, which are common challenges for both tight gas reservoirs and condensate gas reservoirs. In the near-well area, the liquid phase blockage problem due to water phase retention formed by capillary spontaneous imbibition of invasive water and oil phase accumulation due to retrograde condensation precipitation has become a key obstacle to the efficient development of tight condensate gas reservoirs. Experiments were conducted to evaluate the damage of liquid phase blockage under different conditions near the wellbore area. The results show that when the liquid phase saturation in the near-wellbore area increased to 80.12%, the relative permeability of the gas phase decreased to 0. It is concluded that the mixed wettability of formation rocks, ultra-low water saturation, abundant hydrophilic clay minerals and high capillary resistance of micro-nano pores are the main causes for the easy adsorption and retention of liquid phase. Reduced pressure transmission capacity and irreversible formation damage induced by liquid-phase blockage are the two major controlling factors for the low liquid phase flowback rate. It is suggested that developing a flowback system based on the formation physical properties differentiation to control water phase invasion, and changing wettability or injecting thermochemical fluid to control condensate blocking are feasible methods to relieve liquid phase blockage damage in tight condensate reservoirs. Cited as: Wang, Y., Kang, Y., Wang, D., You, L., Chen, M., Yan, X. Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs. Capillarity, 2022, 5(1): 12-22. https://doi.org/10.46690/capi.2022.01.02

Dik ve Yatay Kuyuların Tight Gaz Kondensat Rezervuarında Kuru Gaz Enjeksiyonlu ve Enjeksiyonsuz Üretim Performanslarının Karşılaştırılması

In this study, the comparison of dry gas injection for vertical and horizontal production well scenarios are investigated by means of conducting a reservoir simulation study for a tight condensate gas reservoir. In order to conduct this study a reservoir pattern has been defined. The selected reservoir pattern is 420x420 m in areal extend and 50 m in thickness. All of the necessary reservoir rock properties, and fluid specifications together with reservoir fluid compositions have been determined considering the data available in the literature. A professional reservoir simulation computer program has been utilized for the realization of this study. The well directional trajectories are determined through a dedicated drilling and completion study. The study proved that horizontal wells are much effective in drainage mechanisms in comparison to vertical wells by the fact that dry gas being able to efficiently reach to horizontal drain sections to prevent condensation of oil in the formation for gas condensate reservoirs. The literature contains research on influence of horizontal well on the retardation of the oil condensation inside the gas condensate reservoirs. This research study is conducted to fill the gap in literature in relation to comparison of the well performance of the vertical and horizontal wells during the dry gas injection.

Bridges of Calcium Bicarbonate Tightly Couple Dipolar Lipid Membranes.

The interaction between lipid membranes and ions is associated with a range of key physiological processes. Most earlier studies have focused on the interaction of lipids with cations, while the specific effects of the anions have been largely overlooked. Owing to dissolved atmospheric carbon dioxide, bicarbonate is an important ubiquitous anion in aqueous media. In this paper, we report on the effect of bicarbonate anions on the interactions between dipolar lipid membranes in the presence of previously adsorbed calcium cations. Using a combination of solution X-ray scattering, osmotic stress, and molecular dynamics simulations, we followed the interactions between 1,2-didodecanoyl-sn-glycero-3-phosphocholine (DLPC) lipid membranes that were dialyzed against CaCl2 solutions in the presence and absence of bicarbonate anions. Calcium cations adsorbed onto DLPC membranes, charge them, and lead to their swelling. In the presence of bicarbonate anions, however, the calcium cations can tightly couple one dipolar DLPC membrane to the other and form a highly condensed and dehydrated lamellar phase with a repeat distance of 3.45 ± 0.02 nm. Similar tight condensation and dehydration has only been observed between charged membranes in the presence of multivalent counterions. Bridging between bilayers by calcium bicarbonate complexes induced this arrangement. Furthermore, in this condensed phase, lipid molecules and adsorbed ions were arranged in a two-dimensional oblique lattice.

Peroxynitrite deteriorates oocyte quality through disassembly of microtubule organizing centers

Previous theoretical studies have suggested that utilization of 3-D imaging to acquire morphologic parameters of meiotic spindles may be useful in infertility related procedures as an assessment of oocyte quality. However, our results show that treatment of oocytes with increasing concentrations of peroxynitrite (ONOO−) caused a dramatic alteration in spindle shape in which morphologic parameters are not measurable or are uninformative in terms of oocyte quality. Metaphase II mouse oocytes (n=520) were treated with increasing concentrations of ONOO−, after which all oocytes were fixed and subjected to indirect immunofluorescence. Oocyte quality was assessed by alterations in the microtubule-organizing center (MTOC), pericentrin location, microtubule morphology, and chromosomal alignment. In untreated oocytes, pericentrin is primarily assembled utilizing the acentrosomal MTOC, which appears as a condensation at both spindle poles. The spindle has a symmetrical pointed barrel shape, assembled around the chromosomal plate at the spindle equator. Oocytes treated with low concentrations of ONOO− (<2.5μM) showed shortening of the spindle apparatus, while pericentrin scatters from a tight condensation to a dispersed cluster around each spindle pole. At higher ONOO− concentrations (>2.5μM) the central attachments between microtubules are strained and bend or unevenly break, and the MTOC proteins are further dispersed or undetectable. Peroxynitrite mediated MTOC damage, which deranges the chromosomal scaffold at the time of assembly and separation, caused the deterioration in oocyte quality. These results provide a link between reactive oxygen species and poor reproductive outcomes and elucidate the underlying etiology, which could be used as a superior biomarker for oocyte quality compared to existing assessment tools.