The optimal semi-analytical modeling for the infinite-conductivity horizontal well performance under rectangular bounded reservoir based on a new instantaneous source function

The main objective of this study is to develop the optimal semi-analytical modeling for the infiniteconductivity horizontal well performance under rectangular bounded reservoir based on a new instantaneous source function.The available semi-analytical infinite-conductivity models(ICMs)for horizontal well under rectangular bounded reservoir in literature were developed by applying superposition of pressures in space(SPS).A new instantaneous source function(i.e.,instantaneous uniform-flux segmentary source function under bounded reservoir)is derived to be used instead of SPS to develop the optimal semi-analytical ICM.The new semi-analytical ICM is verified with ICM of Schlumberger[1]and with previous semi-analytical ICMs in terms of bottom hole pressure(BHP)profile and inflow rate distribution along the wellbore.The model is also validated with real horizontal wells in terms of inflow rate distribution along the wellbore.The results show that the developed model gives the optimal semi-analytical modeling for the infinite-conductivity horizontal well performance under rectangular bounded reservoir.Besides that,high computationalefficiency and high-resolution of wellbore discretization have been achieved(i.e.,wellbore segment number could be tens of hundreds depending on solution requirement).The results also show that at pseudosteady state(PSS)flow regime,inflow rate distribution along the wellbore by previous semi-analytical ICMs is stabilized U-shaped as performance of inflow rate distribution at late radial flow regime.Therefore,the previous semi-analytical ICMs are incorrectly modeling inflow rate distribution at PSS flow regime due to the negative influence of applying SPS.The optimal semi-analytical ICM is in a general form and real time domain,and can be applicable for 3D horizontal well and 2D vertical fracture well under infinite and rectangular bounded reservoirs,of uniform-flux and infinite-conductivity wellbore conditions at any time of well life.

Analysis of pressure falloff tests of non-Newtonian power-law fluids in naturally-fractured bounded reservoirs

Application of non-Newtonian Power-law fluids(e.g.polymeric solutions)for production enhancement in petroleum reservoirs has increased over the last three decades.These fluids are often injected as viscous solutions to improve mobility ratio and enhance oil recovery during chemical flooding.As part of the flooding operation,surfactant(or micellar)solutions are first injected at the leading edge of the flood to reduce interfacial tension between water and oil.Subsequently,a slug of polymer solution is injected ahead of normal water to increase viscosity of the water,improve volumetric sweep efficiency and accelerate oil production.Analysis of pressure tests conducted pre and post injection,to evaluate mobility of these fluids,is more demanding than conventional techniques,which were developed strictly for Newtonian fluids.In naturally-fractured reservoirs,flow of non-Newtonian fluids is more complex due to fracture-matrix interaction which is usually resonated in the pressure footprints.Some models have been developed to aid interpretation of pressure tests,but boundary effects on down-hole measurements due to structural discontinuity and presence of an active aquifer,have not been thoroughly investigated.This article presents an analytic technique for interpreting pressure falloff tests of non-Newtonian Power-law fluids in wells that are located near boundaries in dual-porosity reservoirs.First,dimensionless pressure solutions are obtained and Stehfest inversion algorithm is used to develop new type curves.Subsequently,long-time analytic solutions are presented and interpretation procedure is proposed using direct synthesis.Two examples,including real field data from a heavy oil reservoir in Colombian eastern plains basin,are used to validate and demonstrate application of this technique.Results agree with conventional type-curve matching procedure.The approach proposed in this study avoids the use of type curves,which is prone to human errors.It provides a better alternative for direct estimation of formation and flow properties from falloff data.

Estimating the Properties of Naturally Fractured Reservoirs Using Rate Transient Decline Curve Analysis

Transient rate decline curve analysis for constant pressure production is presented in this pa- per for a naturally fractured reservoir. This approach is based on exponential and constant bottom-hole pressure solution. Based on this method, when In （flow rate） is plotted versus time, two straight lines are ob- tained which can be used for estimating different parameters of a naturally fractured reservoir. Parameters such as storage capacity ratio （co）, reservoir drainage area （A）, reservoir shape factor （CA）, fracture per- meability （ky）, interporosity flow parameter （,~） and the other parameters can be determined by this ap- proach. The equations are based on a model originally presented by Warren and Root and extended by Da Prat et al. and Mavor and Cinco-Ley. The proposed method has been developed to be used for naturally fractured reservoirs with different geometries. This method does not involve the use of any chart and by us- ing the pseudo steady state flow regime, the influence of wellbore storage on the value of the parameters ob- tained from this technique is negligible. In this technique, all the parameters can be obtained directly while in conventional approaches like type curve matching method, parameters such as co and g should be ob- tained by other methods like build-up test analysis and this is one of the most important advantages of this method that could save time during reservoir analyses. Different simulated and field examples were used for testing the proposed technique. Comparison between the obtained results by this approach and the results of type curve matching method shows a high performance of decline curves in well testing.